 Previous Messages |
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Posted By
MMS
on 2021-07-17
07:11:25
 |  Re: Possible 8501 replacement kit?
As discussed, fortunately there are several options now.
-I highly suggest to contact directly MCes(if he has some free time):
all the parts he sent me worked perfectly and was ready really fast.
Currently I use his 8501 compatible solution in my C16, and it is just perfect.
-The 6502A based solution with 512KB RAM (Hannes 256K compatible):
it needs a little soldering if you need the extra RAM:
https://lotharek.pl/productdetail.php?id=257
(remark: maybe the Hannes type of RAM is less future-proof than the software based GEORAM like extension in Sidekick264, programmers do not like Hannes RAM so much)
The rest I did not try, so I cannot comment.
(There could be some restrictions in the 6510 based solutions related to datasette or disc fastloaders, but probably this issue is already solved, at least in some versions)
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Posted By
pcsosuk
on 2021-07-15
13:27:25
| Re: Possible 8501 replacement kit?
Hi Guys,
I would like to ask where i can buy few of this for my PLUS 4 and C16? please help if anyone let me know i will appreciated.
thank you to all group.
Regards,
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Posted By
MMS
on 2019-09-28
04:11:42
| Re: Possible 8501 replacement kit?
For me the first is the 256K project machine and other upgrades in one machine.
Could be bought to parties, even able to run from UPS (the recent aftermarket switching PSUs (for Spectrums) with regulated 9V are also lighter than plus/4 PSU (prone to be defective), and can provide even 2A)
Because C16 has more space, I can load some extra stuff into that.
Plus/4 is more compact, but less like it's keyboard, the cursors, and there are (for me) unnecessary chips generating extra heat inside the smaller body (3+1 ROM, ACIA).
For the defective Plus/4s the "installability", lower cost and and lower heat are the key factors and 85MC01 would fit to these requirements.
Jiffy would be a great extra!
Last month I tested and experienced the speed improvement with SJL264 and I was really blown away!
I have an SD-1541/II, an 1541/II with Jiffy kernal and an integrated MicroIEC natively supports Jiffy protocol.
The first two loads with Jiffy a 42KB program in ~11-12 seconds, while the MicroIEC did it in ~5 seconds.
The last one is blazing fast!
The first two speeds are equal to the Apple speed referred several years ago in a forum topic, why the Apple II could load so much faster?
The answer is: C= machines also need proper "drivers". Jiffy protocol is the compatible answer.
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Posted By
MCes
on 2019-09-27
16:12:14
 | Re: Possible 8501 replacement kit?
"MCes solution is bigger by area and by volume"
It can be true, but my solution absorb less than 1/3 of the original CPU (with related benefits) and it's composed only by 2 chips on sokets that can be replaced without any kind of solder tools or solder ability, and in case of future failure the others solutions that can be seen on the web make no simple to repair them (SMD components)....
My solutions fit inside a C16 and a PLUS 4 too, I tried them and with 85MC01, or with my low profile PLA replacemen, the keyboard cover close without touch them: a lot of PLA substitute on the web are declared also for PLUS 4 (PLUS 4 needs the same PLA logic equations of a C16) but they can't permit the right keyboard cover closure, because they are not thin enough to fit inside a PLUS 4!
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Posted By
candle
on 2019-09-27
14:18:13
| Re: Possible 8501 replacement kit?
actually, MCes solution is bigger by area and by volume
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Posted By
MMS
on 2019-09-24
15:49:07
| Re: Possible 8501 replacement kit?
Thanks for the explanation.
Because right now it has no PSU at all 
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Posted By
MCes
on 2019-09-23
17:19:01
| Re: Possible 8501 replacement kit?
@MMS
no no,
I suggest something as
https://www.ebay.it/itm/DC-DC-5V-3A-LM2596S-Power-Buck-Converter-Step-Down-Module-L6RG-Adjustable/112454542472?hash=item1a2ed02488:g:mhQAAOSwBF1a9U69
Remember that a DC-DC converter (not linear regulator as 7805) use the voltage difference in-out to reduce the input current: the concept is that it preserve the energy from the input to the output (so a very less heat too..), if you need an out of 5V 1A and you feed the converter with 10V than it absorb a little bit more than 0,5A (5v*1A = 5W=10V*0.5A)
Your C16 will absorb half current without any kind of chips modify! (without consider the tape motor current...), so the original PSU will be 50% loaded (55..60%) making it oversized.... the original one!
With a DC-DC converter a significative IN-OUT voltage drop isn't a problem!
Why looking for another PSU?
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Posted By
MMS
on 2019-09-23
17:00:09
| Re: Possible 8501 replacement kit?
wow, thank you for the suggestion.
Actually you mean 9V - 5V DC converter, right? like these ones?
1) https://www.ebay.com/c/2114908832
2) https://www.ebay.co.uk/itm/263325140035
Or do you have any suggestions that may fit into the place and your already tried out?
BTW I am considering to buy a regulated 9V DC 2A "generic" PSU as a source.
I suppose it will give less task for the regulator (as the unregulated input voltage could go up to almost 12V depending on the load AFAIK).
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Posted By
MCes
on 2019-09-23
16:39:21
| Re: Possible 8501 replacement kit?
@MMS
I'm working around a very special jiffy modify, if you can wait I think that you will loving it..... 
Into C16 you can also cut out the 5W 20 OHM resistor (the white ceramic one) and replace the 7805 regulator with a 5V dc-dc converter: the current absorbed from PSU will be lowered dramatically! If you need half of power: your old PSU become twice strong than what do you need...
And the saved energy is energy that won't be dissipated inside the machine....
The best way to cool a computer is make that it not generate heat!
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Posted By
MMS
on 2019-09-23
14:47:50
| Re: Possible 8501 replacement kit?
So I preordered my candle/Lotharek replacement, and will have a C16 soon.
C16 has enough space and less IC inside, so the heat is a smaller issue. Will be hooked up with a ZX Spectrum128K PSU (compatible with C16). It was a long time dream to have 256K
After finishing that below special project I still need to repair 3 of my dead Plus/4s and get a proper "square connector" PSU for them. Probably one or two of them has 8501 defect, than I plan to buy the cheaper (and smaller?) 85MC01.
OFF
Plan to add to the C16 a Jiffy and probably an internal microIEC, than may no external house cutting and may behave as an internal HDD. :-D
As per my tests, the microIEC is a beast linked with JiffyDOS or with SJL264 from BSZ. Close to 10KB/sec loading speed, and B does not mean bit Certainly it is less compatible than SD2IEC or SD-1541/II, but faster than those, and can be integrated into the housing without any sign.
Actually the only downside of C16 os the missing UserPort, so cannot connect a wifi modem (or my RS232 mouse even if I ever finish it ) so cannot try out the BBS. On the other hand the more easy assembly and the lower heat (except regulator) are real benefits, and even has space to add a proper internal (but silent) cooling, but the space need to be measured.
I think the ZX Spectrum PSUs may be able to manage the extra load of th PC fan, while the Plus/4 PSU has it's own limitations. (1.5A on mainly used 5V line, while ZX 128K has 1.85 or 2.1A on 9V, regulated internally to 5V). Hopefully C16 regulator can manage it.
I may buy a professional PSU for Plus/4 40-50USD + shipping, but can easily buy a 2A 9V regulated PSU for Spectrum for 20€ with shipping, or try to find a strong ZX +2 PSU from UK (25-30€)
C16 keyboard is very robust too.
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Posted By
MCes
on 2019-09-09
15:31:46
| Re: Possible 8501 replacement kit?
It's arrived.....
The 85MC01: the C-MOS substitute for 7501/8501!
more informations (also about availability):
http://www.amibay.com/showthread.php?106203-8501-replacement-for-C16-Plus4-work-in-progress
85MC01 is a C-MOS version, so it need less current (so less heat inside computer..) but it can't execute the illegal opcodes,
for this reason who buys it has a week to test it and send it back: when it will be arrived back I'll refund the cost of 85MC01 (but not the shipment cost).
Who is interested can contact me directly, thanks
 
 
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Posted By
candle
on 2019-09-03
19:49:36
| Re: Possible 8501 replacement kit?
this one uses nmos 6502a cpu, so there should be no issues with illegal opcodes
all software i've tested behaved the same on this board and genuine 8501 cpu
i plan one more expansion board for plus 4, but i have too many open projects right now to just start yet another one ;(
sd2iec experience was a total letdown, and i've ended with 1541 drive and sd2iec as a source medium to copy to psyhical disk, thus makes me wonder, why noone have developed some kind of internal drive like "side" cartridge for atari
closes to this i've seen was hardware used in one demo i've saw on youtube (micromorph0s1s)
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Posted By
MMS
on 2019-09-03
17:05:54
| Re: Possible 8501 replacement kit?
Dear candle,
Great news, that we may have the CPU replacement with a cooler (?) and more reliable CPU, and the 256KB RAM upgrade itself validates the price.
I am really excited to see how it will work.
I will definitely (pre)order one for the working machine, and need a different (square) connector PSU to able to doublecheck my other defective machines, if they have CPU defect, or other issue (TED, PLA, ROM, RAM, just to name few )
I am pretty sure, that the 256KB RAM expansion's easy avaliability (compared to machine motherboard rework at some distant place + risks of shipping) will boost the 256KB compatible releases. I am really excited to see an adventure game with cached pictures
Linking it with a Jiffy drive or IEC could be a beast
Certainly the list of compatibility is an interesting point, if illegal opcode was used on not.
Maybe it could be a "feature" or "effect" of the SWs in our database to be "illegal opcode free" :-)
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Posted By
candle
on 2019-06-18
15:49:00
| Re: Possible 8501 replacement kit?
16MB REU is in form of Ultimate 1541 or/and Cameleon cartridges
they contain FPGA chips with implemented SDRAM controller plus 16mbytes of SDRAM
6502plus4 contains small CPLD chip far inferior to what is used in these mentioned before, and, in such limited space chances for that are slim, i would need to resort to 0.5mm pitch BGA packages both for RAM and rest of the logic, power supply would require more components too, as FPGA chips are using at least 2 (more commonly 3) voltage rails for power, the board itself would have to be at least 4, possibly 6 layers of copper just to get escape routing done of such FPGA
this suppose to be as cheap as possible, but i don't know what the final price could be
next thing for plus4 i'm going to do is pla/rom replacement, possibly with SID in one form or another (i've made some work with FPGA SID implementations years ago, with SoundBoard project for Atari)
anyways, FPGA chips can be inexpensive and fairly simple to use, don't get scared, but if you need it to be small and cheap it will be either one or another, not both
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Posted By
Spektro
on 2019-06-18
14:43:14
 | Re: Possible 8501 replacement kit?
Hi candle,
There is a 16MB RAM expansion for the Commodore 64, or so I've heard :) Any chance your 6502 plus 4 board could evolve to carry that much RAM?
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Posted By
candle
on 2019-06-18
04:12:25
| Re: Possible 8501 replacement kit?
ha ha
i don't know what retail price will be, most of the things i've designed as a hobby goes to lotharek.pl as he handles all the logistics, assembly, and keeps everything avaliable
this is the main reason that ultimate1mb board became a de-facto standard for 8bit atari - there are no batches, but costant product supply, thus one can buy something whenever one needs to, no once in a lifetime deals there
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Posted By
MCes
on 2019-06-18
03:45:30
| Re: Possible 8501 replacement kit?
@candela wrote: "here is my five cents to 8501 replacement kit"
Wonderful!
Also I when I'm projecting use the economical compatibility as a target, and 5cents is a very low price.
As a PLUS4 and C16 owner I'm happy to buy from you 20 pieces: 1$ (or £, or €, or... else?)
Where it's possible to bought it at this price?
Thanks
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Posted By
MMS
on 2019-06-17
18:05:47
| Re: Possible 8501 replacement kit?
Guys, you all are fantastic!
Some years ago reading through the issues, and seeing my dead Plus/4s, I tough the time will come, when we could use only emulators, and the still working Plus/4 price will go up like a rocket.
Now the top issues mapped, and most of them solved. Situation improves: we should not cannibalize the defective Plus/4s for still working parts, but seems we may revive more and more of the dead ones.
We may have now new PLA, new 6502based 8501, internal 64K RAM expansion for C16, exchange the ROMs to new ones, have SID card, even JiffyDOS or even 256KB RAM (I ould not believe it will happen), and we have a properly working fastloaders and some really good SD card based devices. (and there is a running TED project)
I think the knowledge and interest that is lost at the closure of the "classic" 264 period, seems regained again.
These are really good news, and because I am also a fan of the 264 series, it makes me really happy. 
Thank you all for your hard work and I congratulate for achieved results!
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Posted By
MMS
on 2019-06-17
17:49:49
| ys,Re: Possible 8501 replacement kit?
Gu
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Posted By
candle
on 2019-06-17
16:55:58
| Re: Possible 8501 replacement kit?
here is my five cents to 8501 replacement kit
https://youtu.be/1e0n6eZzYc4
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Posted By
MCes
on 2019-06-16
06:15:08
| Re: Possible 8501 replacement kit?
Good news: my friend tested it on C16 and on PLUS4 with cassette/floppy/self-turbo/presentations/ecc...
With original processor or with my replacement kit: the same behavior!
It's better than what i was hoping, bacause the absenze of illegal op-code make it not 101% compatible (100% is LEGAL, 101% is ILLEGAL....  )
but I'm happy that this absenze make damage so limitaded to be not detected in stress-test!
The C-MOS technology of the new CPU make a gift: now my Commodore is absorbing 80mA less!
Less current, less heat inside computer, less temperature inside computer: other fragile chips inside the computer can having better life (PSU also...)
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Posted By
MCes
on 2019-06-06
12:13:34
| Re: Possible 8501 replacement kit?
@MMS: thanks for your words...
A friend of mine will start a "stress test" period with a lot of games/peripherals (old and new), I suppose that he will start at weekend....
He will tell us if this project is stable as it seem to be.
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Posted By
MMS
on 2019-06-06
15:53:05
| Re: Possible 8501 replacement kit?
Thank you for the info!
Very nice stuff, especially you are looking for the price and compare it to other possibilities too.
I mean we are very lucky some ppl like you working on the perfectly working solution.
Thank you!
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Posted By
MCes
on 2019-06-03
13:04:39
| Re: Possible 8501 replacement kit?
ok:
I have a stable release that preserve also the port registers mirror ram (can be useful only in C16...),
now it need some stress test ( a friend of mine can be the right guy to do it... )
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Posted By
MCes
on 2019-05-18
13:12:06
| Re: Possible 8501 replacement kit?
Sorry....
"Alcune informazioni ed evoluzione sul mio progetto di pseudo-8501" = "Some information and evolution about my project of pseudo-8501"
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Posted By
Csabo
on 2019-05-17
17:49:14
| Re: Possible 8501 replacement kit?
Hi MCes,
Your posts are inadvertently getting caught by the spam filter because you're attempting to post 3 links in one post, something that is unfortunately very common in actual spam posts sent by bots. (I updated the site's message about this, hopefully it's now more clear.)
You can either just post the image links without the "https://" part (and someone will fix it for you), or post all your images into one gallery in a place like "imgur".
Good luck!
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Posted By
MCes
on 2019-05-17
16:27:22
| Re: Possible 8501 replacement kit?
in optimization....
https://postimg.cc/N2G5BFFJ
https://postimg.cc/KRR8NdMM
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Posted By
gmc
on 2018-12-30
14:35:10
| Re: Possible 8501 replacement kit?
Also interesting to know if anyone has tested on the these fpga kits.
Seems the 8501 is almost impossible to find now.
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Posted By
Ramtop
on 2018-04-02
07:57:47
| Re: Possible 8501 replacement kit?
Has anyone tried one of Piotr Bugaj's 8501 replacements yet? I see it's now listed on Sell My Retro for £40.
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Posted By
Hypex
on 2018-03-25
08:20:46
| Re: Possible 8501 replacement kit?
I recently discovered a 6510-1 that has an 8-bit I/O port. Perfect for use! Unfortunately it looks to be rarer than an 8501 itself so not much better.
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Posted By
MMS
on 2018-03-18
18:23:21
| Re: Possible 8501 replacement kit?
Hi Ramtop, thank you for the detailed answer!
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Posted By
Ramtop
on 2018-03-18
13:24:08
| Re: Possible 8501 replacement kit?
I built my own 6510 board last year for testing and no disk fast loaders would work with it. Port $01 on the 6510 only has 6 I/O lines, mapped as bits 0-5. Bit 6 and 7 are not connected and unfortunately those are the bits used on the Plus/4 and C16 for serial port clock and data.
The 6510 cards on ebay reroute the serial lines to bit 5 (which isn't connected on the 8501, but is on the 6510) and the bit normally used for cassette motor control (bit 4 I think, but I may be wrong). The hacked kernel supplied with those cards patches the disk I/O routines to use the new port layout, but obviously fast loaders bang bits 6 and 7 directly and will fail to work.
From testing with my own 6510 card the only thing that is compatible with the 8501 I/O port on a hardware level (ie, when bypassing the kernel) is cassette loading. Nothing else. That's why I abandoned the 6510 and started work on a 6502 card, as 6510 boards seem to just be a semi-compatible hack. The 6502 card, when all the bugs are finally exterminated, should be pretty close to 100% compatible with the 8501.
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Posted By
MMS
on 2018-03-15
16:33:03
| Re: Possible 8501 replacement kit?
Actually I started to read the 6510 based board text in details, and I saw, that it is not only the casette playback cannot be stopped (it could be something less important).
In the documenation it is mentioned, that the disc fastloaders will probably not work. That one is a bigger problem, as a lot of converted games, newer games or demos use built in fastloaders with 1541. (not to mention my slideshows )
Could anyone confirm, how far this limitation go? None of them work, or only few of them?
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Posted By
Ramtop
on 2018-03-13
07:12:40
| Re: Possible 8501 replacement kit?
As far as I'm aware it is indeed impossible as the 6510 doesn't read or write via data bus during access to the I/O ports.
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Posted By
Hypex
on 2018-03-13
03:14:54
| Re: Possible 8501 replacement kit?
@Ramtop
I'm aware of this but somehow read your post as 6510. Or I wouldn't have asked.
I wonder now if a 6510 can be hacked, so to speak, to provide an 8-bit I/O port. Probably not.
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Posted By
Ramtop
on 2018-03-09
09:14:11
| Re: Possible 8501 replacement kit?
@Hypex, By using a 6502 It doesn't have the $00/01 port, so I can implement that completely in the CPLD.
@Hege, I was thinking more about timing problems interfacing the FPGA with the C16/Plus4 hardware, rather than issues with the software core. When I started work on my 6502 card I really wasn't prepared for how touchy the 264 family are about bus timing.
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Posted By
Hege
on 2018-03-07
02:00:03
| Re: Possible 8501 replacement kit?
Sure. The most problematic is to generate the composite video signal. I might use a support chip beside the FPGA to generate proper PAL/NTSC composite video. Beside my plan is to have the VGA/hdmi output so that we can hook it up to a modern display.
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Posted By
MMS
on 2018-03-06
17:44:35
| Re: Possible 8501 replacement kit?
TED revival project: "it's alive"!
A lot of dead Plussy waiting for this magic moment
I have one dead TED and 2 dead 8501 in my Plussies.
It will be an expensive hobby, but who cares?
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Posted By
Hege
on 2018-03-06
15:11:33
| Re: Possible 8501 replacement kit?
It is not the timing which is an issue. In my FPGATED C16 (and plus4) I am using a soft 6502 core with a 8501 wrapper and its timing is perfect. I can use an 1541 drive with fastloader without issue. Setup and hold times can be met in an FPGA design. It is rather the illegal instruction implementation which might lead to some incompatibilities. Even if illegal instructions are implemented there are some which depend on the dynamic latches of the IC technology. These dynamic latches are difficult to simulate although not impossible.
An FPGA bvased 8501 implementation is not that difficult. The 6502 core exists, the wrapper I have in my C16 FPGA implementation. I just never had time to build it... I am going to build the TED replacement first.
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Posted By
Hypex
on 2018-03-05
08:19:38
| Re: Possible 8501 replacement kit?
@Ramtop how are you able to map the I/O to $0/$1 when the 6510 handles this internally?
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Posted By
MMS
on 2018-02-26
16:16:46
| Re: Possible 8501 replacement kit?
That's why I asked, how well it works with recent demos, FLI pictures. There were some guys ordered few pieces, so we will know. He showed a demo running,it was Perfect Visons3 Part2, I dunno how demanding that demo is.
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Posted By
Ramtop
on 2018-02-26
06:07:37
| Re: Possible 8501 replacement kit?
So he's using an FPGA with a softcore?. Timing will probably be an issue.
That's hard enough to get right even with a real 6502. I've been working on a 6502 card for the Plus/4 for about six months now and haven't been able to get the timing exact enough to display FLIs correctly, or run fast loaders with an SD2IEC. That's using a physical NMOS 6502 with a Xilinx CPLD providing AEC, the IO port, etc.
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Posted By
Hypex
on 2018-02-23
05:55:39
| Re: Possible 8501 replacement kit?
I like red. It looks nice and PCB's were due for a colour change. But it doesn't match the classic green of the old boards.
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Posted By
MMS
on 2018-02-19
14:55:17
| Re: Possible 8501 replacement kit?
yes, I work in quality, and never use red color, only if I want to scrap something
Green is OK for me...
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Posted By
Hypex
on 2018-02-19
08:30:18
| Re: Possible 8501 replacement kit?
Red and green should never be seen. Except when it fixes our machines!
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Posted By
MMS
on 2018-02-18
06:26:47
| Re: Possible 8501 replacement kit?
Hello Guys,
Just recently on Facebook Commodre Plus/4 section a new guy (Piotr Bugaj) started to promote the Xilinx Spartan based 8501 kit he assembles. (it is based on Mark Smith's project)
Piotr attached some pictures running Saboteur by this Xilinx based machine and he pictured he has some boards.
Some ppl already odered few pieces, I am waiting for the test results how they perform when high cycle accuracy required (recent demo, IHFLI, HFLI). Then I will jump in with two boards too. No heatsink required.
The price he menioted was 40 GBP (or lower if more ordered) plus shipping.
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Posted By
filker
on 2018-01-16
05:36:28
| Re: Possible 8501 replacement kit?
Yes. The same guy mentioned in the first link given in this thread sells them.
BTW, I was planning to do it on my way, and last night I examined the original kernal to see the modifications necessary for 6510. 6510 has no last two bits at the $01, which are used by the kernal with a tight code, such as:
BIT $01
BVS ....
or
LDA $01
ASL
BPL ....
These code snippets cannot be changed in place since we can only use the bit 3 and bit 5 instead (for serial data and clock inp). So, an ugly patch is needed in these codes.
Though, I'll also examine the jiffydos kernal, I hope it is less harmful to change it.
BTW, since we use 6510 in Plus/4. I first changed the default screen, border and text colors in the kernal ($334D, $3351, $187F) to C64 colors: $16, $46, $16.
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Posted By
filker
on 2018-01-12
16:00:28
| Re: Possible 8501 replacement kit?
At last, about two decades later, I repaired my problematic Plus/4. It was working only when it's cooled down to ~0 degree Celsius!.. It turned out that the 6551 was the problem. I had checked it years ago and desoldered its +5V though. Only the complete removal of the 6551 solved the problem (after inspecting all the traces and changing almost all the diodes, caps, RAMs, etc.).
Anyway, now I can try this modified 6510 in place of 8501. I'm planning to mod the kernal by myself for serial I/O remapping.
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Posted By
Imperious
on 2018-01-10
19:16:19
| Re: Possible 8501 replacement kit?
I've purchased one of these 6510 to 7501/8501 kits. It will likely take a couple of weeks to arrive.
I'm planning on doing a Youtube clip when I have installed and tested it a bit.
Don't expect anything too professional though as I'm a newb when it comes to Youtube video creation.
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Posted By
Hypex
on 2018-01-10
10:35:39
| Re: Possible 8501 replacement kit?
Where did you locate your CSG 8501?
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Posted By
CPlus/4user
on 2018-01-04
03:24:35
| Re: Possible 8501 replacement kit?
Thanks for the answer. I purchased CSG 8501 after the failure of my MOS 8501R1 (overheating). When I will put it in and check how it heats up.
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Posted By
crock
on 2018-01-03
17:54:27
 | Re: Possible 8501 replacement kit?
The answer to that is somewhat subjective but empirical evidence would suggest yes.
Some of us on the CBM hackers list did some measurementts a few years back to determine the current draw and temperature of the various 7501/8501 CPU revisions that we could find. The results were that the later CSG branded 8501's ran 10-12 degrees cooler that the typical MOS 8501R1's. With no heatsink the CSG chips we tested (datecode 1490) ran at around 46 degrees, as opposed to the MOS chips which varied between 57 and 62 degrees.
I can't speak for an 8501R4 as that was not a revision included in the tests, but there were 8501's (with no revision) dated 1087 which ran just as hot as the early ones.
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Posted By
CPlus/4user
on 2018-01-02
18:19:58
| Re: Possible 8501 replacement kit?
Is CSG 8501 better than MOS 8501R4?
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Posted By
Hypex
on 2017-11-25
01:19:04
| Re: Possible 8501 replacement kit?
Thanks for the chippy condolences. Compare to eBay CPU chips these were half the price so I could get two for one eBay price. When it was a month ongoing I new something was wrong. I'll just have to remain a soft C16/Plus4 user for now. With my broken Plus/$.
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Posted By
MMS
on 2017-11-07
19:03:53
| Re: Possible 8501 replacement kit?
Really sorry to hear your troubles.
In the past I ordered several things from Aliexpress, and all arrived in a relatively short time, and without problem though I know these are different guys and companies behind the surface.
(controller, xbox chatpad, simple VR headset, arrows, midi connector, even xbox HDD,)
(PS I had similar experience with Dinodirect (after some OK buys), and then I stopped ordering from them. But never had similar experience with Aliexpress)
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Posted By
Imperious
on 2017-11-07
05:54:32
| Re: Possible 8501 replacement kit?
Twice I tried ordering 8501's from Aliexpress, but it was a few years ago. There were sellers selling 5 for $38 or therabouts. Both times nothing ever arrived and I got my money back.
Recently I have noticed the Aliexpress link posted above is now dead, and nothing I have tried in the search bar has brought up 8501's. It is not easy fnding chips via Aliexpress search bar, unlike ebay.
I have a suspicion that Aliexpress have purged a lot of the smaller sellers as it appears harder to find various items than it was a year or even 6 months ago.
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Posted By
Hypex
on 2017-11-06
23:04:48
| Re: Possible 8501 replacement kit?
@MMS
I've taken your advice and ordered two samples for my use. I expect them to come next week. I've got my heatsinks ready to go. So thank you also for those guides including Whirlpool I'm quite familiar with. In addition I have one spare TED with the hope that one other TED is working. And hope that if one chip is fried already in testing that it doesn't take the new one with it. I've heard stories that one bad chip can kill another. Eeek!
Update:
Looks like I've done my money and lost two rare CPU chips. I's been almost two months since I ordered. No sign. I suspect I should have set up a PO box as delivery guys have been lazy in the past by leaving things in letter boxes that should have been signed for. Every time I tried to look up tracking there was no information. I had trouble signing in at one stage and lost the dispute window. So the system automatically assumes the order arrived without you confirming so. Not happy.
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Posted By
MMS
on 2017-09-05
15:28:17
| Re: Possible 8501 replacement kit?
Partially OFF:
It is a little old article about spreading the proper quantity of thermal grease. (at the time of 200W Pentium 4s it was much more crucial, than nowadays with 35W i3s. Yikes!)
http://www.tomshardware.com/reviews/thermal-paste-heat-sink-heat-spreader,3600-5.html
Actually I do not suggest to use silver or aluminium based thermal paste.
Maybe Artc Silver only, as it is not a conductor.
Because if you overdone it, then it may flow down from the surface of the IC, and may cause short circiut (or just strange working) IC between the legs. PPl using them need to clean them off properly.
http://forums.whirlpool.net.au/archive/1730434
Anything above 8 W/(mK) is pretty good.
Artics are good, Thermal Grizzly is good (they even have thermal pad/strips with very good results, some is >10). I have no data about Noctua, but pretty good.
FujiPoly is one of the major industrial players, they have products (pads) have >17, that is really unusually high in this industry.  But price is like hell.
and some suggestiosn from real users. Not all prefer the Noctua, but some do.
https://linustechtips.com/main/topic/319365-thermal-paste-nt-h1-vs-arctic-silver-5/
And finally a REAL test, hopefully not a sponsored one :-):
https://www.techpowerup.com/reviews/Noctua/NT-H1/4.html
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Posted By
Hypex
on 2017-09-05
10:10:39
| Re: Possible 8501 replacement kit?
@Imperious
Wanted to thank you for the information you dug up there. I don't know how you identified any chips at all. I've examined the pictures and in the large JPG where the chips are visible it looks like someone has taken a small picture and blown it up digitally. It just goes into a square blur when I look at it in actual size.
I don't know where you found this Ferix guy from. I can't find any info on him on the net. Nothing C16 related shows up. A missing P5 shouldn't corrupt any data but I don't know if it would cause instability if there are loose TTL lines left floating.
What would be cool is if a working circuit could be put on a cartridge. Plug in a cartridge. CPU fixed! Or in the least a CPU tester. An external 6502 CPU being able to pull address lines and read memory would be good to test.
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Posted By
MMS
on 2017-08-27
14:58:57
| Re: Possible 8501 replacement kit?
@filker
in the factory I work we use 2 Peltier cooling element on each production line to keep the soldering paste at~25°C.
We have 12cm fans on them, and still te Peltiers die rather frequently, at least yearly we have to exchange each of them. If you do not cool is properly (on the hot side), it could overheat very fast.
(BTW this soldering paste cooling method developped ~12 years ago, and I can say it is rather advanced for it's age).
The heatpipe is nice as it could be a passive element, and the inside liquid's phase change itself transferring a lot of heat from the IC.
Usually they use a fan to cool down the gas, but I suppose, that from 8501 the linked thin (and long) heatpipe with a normal heatsink (outside the hot Plus/4) could be enough.
The only thing I do not know, how we could prove it is cool enough, and the cooling is efficient enough?
What is cool enough for the 8501?
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Posted By
ken
on 2017-08-25
12:06:51
| Re: Possible 8501 replacement kit?
if you use the short Header connectors and flush mount machined inserts you can make a board that has more than enough clearance
I just tried a 28 pin adapter board in the socket and closed the cover , then looked into the rear user port and could fully see across the top of the eprom and it was not touching the keyboard
so a no soldering needed adapter can be made
ken.
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Posted By
Imperious
on 2017-08-25
09:22:51
| Re: Possible 8501 replacement kit?
Well it appears I have less information on this than I thought. A lot of it was in my head, with respect to figuring out exactly what ics this Ferix guy used.
It looks like because He has used a WDC 65C02 with a BE line, he has left out the 74LS541's from the 6502-8501 schematic. I'm not sure whether he has used a 74LS682 and 74LS688 for the 6522 chip select, or used 2 74LS688's.
As I mentioned earlier it looks like he has tried to recreate the gate-in function, from what I can tell using a 74LS74 along with another logic chip I cannot identify. I can figure out he has used a 74LS00, 6522, 65C02, 74LS688x2 OR 74LS682, 74LS245, 75LS74.
I also can tell the Ferix board has just left P5 hanging there. He does show a photo of the c16 boot screen but no proof whatsoever that any of the external data ports are working.
http://www.filedropper.com/plus4-8501
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Posted By
filker
on 2017-08-25
05:58:14
| Re: Possible 8501 replacement kit?
Thanks @MMS. Although I've checked all solder joints with a magnifying glass, it was a check in a cold state... I'll check that parts you've mentioned. It's certain that I miss something.
By the way, I bought a peltier today And burned it immediately!  I was measuring the temperaures of the sides, and it popped in less than a minute. It really needs a big fan (which isn't a case for plus4), and didn't like the power I supplied from a 12V 7A gel battery.
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Posted By
MMS
on 2017-08-24
20:41:08
| Re: Possible 8501 replacement kit?
@filker
OFF I had a Apple G4 motherboard, when it got warm, one of the IC legs on the corner separated (due to torsion happened on IC due to heat) from the motherboard, as the soldering was broken (in fact it was the top1 faiilure mode of that laptop range, and seems to be a design issue).
When I pressed hard the top of that component (it was an inverter IC), then the laptop still worked.
From the sympthoms and the list of exchanged (and OK) parts does not look anything serious, but something that plays a role in the RAM refresh process and in warm condition do not make this. Missing this regulatar updates, the DRAMs start to loose their information after some time.
Unfortunately I am not a HW expert, but worth to check that part of circuitry, looking for a loose / cracked soldering on an IC or component leg.
The Mac case:
http://macintoshhowto.com/hardware/how-do-i-get-my-broken-g4-ibook-fixed.html
(hopefully somehow you can use it to find the failure mode and able to get back the Plus/4 from sub zero state)
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Posted By
RobertB
on 2017-08-24
15:40:42
| Re: Possible 8501 replacement kit?
Hypex wrote:
> Nice. Do you have pictures on your blog I may have missed?
No, I haven't posted any pictures of that. I'll try to remember and do it when I get back to California.
Writing from Portland, Oregon,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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Posted By
Hypex
on 2017-09-05
10:12:50
| Re: Possible 8501 replacement kit?
@MMS
That's funny. A Plus/4 might look even cooler with those fans spinning on the back! I got another email back on the RFQ. Almost 50 euro for an 8501R1. The 35 euro for the 8360R2 is looking good. So decided to take your lead and order from Ali. Put myself down for two. Will see how it goes. Now that Australian company flat pipe is just what I want on my Plus/4! Even without water or air cooling that should do it good. Looks and acts cool on the inside.
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Posted By
filker
on 2017-08-22
05:53:06
| Re: Possible 8501 replacement kit?
A fan is good idea. Though I need a peltier or something similar for my Plus/4.
I cool its motherboard in the refrigrator first in order to be able to use it for ~5 minutes!.. As it warms up, the screen starts to fill up with @s, and crashes eventually.
Couldn't figure out the problem. CPU and TED works in another machine. Changed all RAM, sockets, capacitors, PLA, removed func. ROMs, Basic etc. inserted the diagnostic ROM instead... No luck yet. It likes sub zero temperatures.
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Posted By
MMS
on 2017-08-21
19:38:56
| Re: Possible 8501 replacement kit?
Fan on a Plus/4 is like putting a fan on a Formula 1 car
Actually I think without heatsink the R4 should be more reliable, but with a proper heatsink?
I think after that the R1 should be as reliable as the R4, and the R4 should work till the next century.
(Heatpipe: it was just a joke. I designed few years ago a very slim computer, and heatpipe with the proper radiatior + very slim fan requires at least 40-60mm extra height for the cooling, and it is a bare minimum. or you need special horizontal design (like seen in some HP laptops) )
or just for an idea (this is an Australian company):
http://www.ebay.co.uk/itm/Heat-Sink-Pipe-Flat-Plate-1-2-20-100mm-Thermal-Aluminum-Cooling-LED-CPU-IC-GPU-/272635305655?hash=item3f7a549eb7:g:UAsAAOSwSypY9YjS
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Posted By
Hypex
on 2017-08-21
12:48:50
| Re: Possible 8501 replacement kit?
@RobertB
Nice. Do you have pictures on your blog I may have missed?
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Posted By
Hypex
on 2017-08-21
12:46:25
| Re: Possible 8501 replacement kit?
@Imperious
Yes using a BE line should be good. I've also wondered about the TTL levels. And if they match. Perhaps some looking up for any difference between MOS 6510 and WDC 6522 parallel port will help. The circuit is proven, AFAIK, for 6510 and 8502, but it is old.
Another thing, what did you do with the missing P5? I've read TTL chips don't like floating pins so if it is left at NC it can cause instability. Did you tie it to ground to keep it at zero?
Did the Spanish forum guy post any diagrams or pictures? I look forward to seeing your extra pics and docs.
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Posted By
RobertB
on 2017-08-21
02:33:32
| Re: Possible 8501 replacement kit?
Hypex wrote:
> 4.) Should a fan be put into the Plus/4?
Already have one in one of my Plus/4's.
Courtesy of Ray Carlsen's handiwork,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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Posted By
Hypex
on 2017-08-21
01:18:47
| Re: Possible 8501 replacement kit?
@MMS
Yes thank you for the welcome. Suppose I should open a thread to introduce my self since I'm rather a stranger in these parts. And soon one day hope to to realise the teenage dream of having a Plus/4.
1.) Yes your likely right. Think I take advantage and get me some.
2.) (Haha. I hear what you mean. I do agree. I got a bit obsessed when I found it. I sent off some RFQs just for interest. For quantity of ten. I only got one email back so far, from another German site, giving me a price of about 35 euro a piece. For an 8360! I don't recall looking for a TED. :-?
3.) That's some good advice there. Is there a FAQ here you could add those tips?
Personally I've always wondered if an active cooler on any IC can increase risk of damage. A heat sink is passive. But for active cooling, you have two opposing forces, heat and cool, coming together on the IC. That would look to cause stress and fracture structural integrity. Perhaps it's fine.
4.) Should a fan be put into the Plus/4? It would match the fins outside the case.
5.) I thought an 8501R4 would be unheard of until I saw it listed. But would it be any better? Would C= have finally have fixed the manufacturing process to match the proven 6510?
6.) I read about this and it is a concern. I was given a Plus/4 years ago from an Amiga guy who used to go to my Amiga club. He couldn't find the PSU. I opened it up and the whole board was stripped. If it had a CPU I didn't see it. I have another one I've confirmed as broken from a broken black screen.
My soldering was better when my eyesight was but I wouldn't want to solder a computer board. Even an older one. Perhaps I should just have ago against the rarity of working boards. Still, a Plus/4 would be easier than doing SMD. I could do the C64 PSU "fix" but I rather like the trendy square connector. And C64 owners are still looking for reasonable plug-in replacement for their very popular computer.
That CPU in a cartridge is looking good against accidental DIY damage.
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Posted By
MMS
on 2017-08-20
07:15:00
| Re: Possible 8501 replacement kit?
Off: Yeah, like a mini Kickstarter or what
Some of the parts became (or always was) really expensive (user port connectors, microcontrollers, special ICs), and it slows down or make impossible to realize working projects.
Sometimes the most talented HW people do not have enough free money to risk on projects with questionnable final result and limited user base. ( I am almost the opposite )
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Posted By
Spektro
on 2017-08-20
02:56:16
| Re: Possible 8501 replacement kit?
Off topic:
Regarding the MMS's group purchase suggestion... Maybe the 264 scene should have some kind of a co-operative
Its members could invest some money to get the most wanted hardware projects materialized (CPU replacements, custom ROMs, memory expansions, SID cards, 3D-printed parts, and so on), or collect a stock of spare parts, or pay for the forum's domain name etc.
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Posted By
Imperious
on 2017-08-19
22:52:41
| Re: Possible 8501 replacement kit?
@Hypex
My apologies, as I should have mentioned I already tried putting the data ports in their correct place, still nothing worked. The point of using either a WDC 65C02 or the 65C816 is that it has a BE (AEC) line, and therefore the 74LS541's then are not needed to recreate that.
There is a possibility using HC and HCT logic chips are causing an issue due to the difference between logic levels as opposed to LS ic's.
I thing the guy on the Spanish forum had a better understanding of all this, he made a proper board up for it. I am an electronics tech, not an engineer, so my knowledge is not good enough for fully understanding this. I have some more pics and docs where I was trying to figure it out, I'll post what I have later and maybe someone can figure out the missing bits.
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Posted By
Hypex
on 2017-08-19
11:45:57
| Re: Possible 8501 replacement kit?
@Imperious
If you look at the CPU pinout he has listed and the associated schematic here you will see it is has a mistake (or two) so I'm not surprised it didn't work. It looks like he based it on the 8502 conversion but didn't fix the port lines to match the 8501:
http://www.webalice.it/gratteri/65028501.gif
He has P0 to P6 listed but the 8501 doesn't have that in sequence, it just matches the 7 line count of the 8502 port. It has (the 8501), perhaps oddly, P0 to P4, with P5 missing, then P6 to P7. I suspect, without inner knowledge, that C=? wanted to match the serial layout of the C64 $DD00 port with DATA at P7 and CLK at P6.
Now, without being corrected, following that circuit, the DATA line is connected to the CLK input and the CLK is connected to NC P5 input! So every time it tries to use serial, DATA will be output on the CLK line and the CLK will be missing! LOL! 
But I have to ask, did the core actually work? It sounds like it did. Just worse than the 6510 hack where serial can actually work.
I'm no electronic expert, having just dabbled in electronics when I was younger, and then slowly got into programming once I got my first computer, a C16. And your board is after my own heart, looks like my past projects. But having studied that circuit and related threads I can see the problem.
Without correcting the diagram, the on board fix should be simple. Reroute P6 and P5 going to the 6522 and move them up a line bit, so the P6 goes to PA7 and P5 to PA6. If you see what I mean. Relabeling the diagram would be more clearer. Hm. DPaint anyone?
Having read about how to turn a 6502 into a simple computer I've come to an understanding of address decoders and what those data lines are for on the 6502. Now it makes sense, in a nutshell, CPU sends out a request to access an address on the lines, then sucks in that location data byte or blows it out.
To simplify the design, since an access to location $00-$01 needs to be detected, what occurs to me is using an OR logic gate. A TI CD4048B CMOS Multifunction Expandable 8-Input Gate can be configured for this as cascade. The address MSB can go into one, output connected to another with the address LSB, then inverted and used as chip select on the 6522. So that when all A15-A1 lines are ORed together, the output will be zero, inverted into a 1 CS flag. A0 goes to the 6522 as usual. A15-A1 go to two IC chips and reduce the lines to just one. If that can work.
The 6522 also seems superfluous to me since it contains a lot of functions, basically being a CIA, but all we need is one parallel port and DDR. I read 6521 dual parallel port lacked something. I don't know what that was, but these days, I would think a WDC 65C02 and 65C21 combo should work.
A 65C816 also seems over the top, since we only need an 8-bit core, and the already extra opcodes of the 65C02 makes it worse, if they are accidentally are on purpose called upon.
If you still have your board, please try the above fix, and see if it works better.
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Posted By
MMS
on 2017-08-19
09:06:54
| Re: Possible 8501 replacement kit?
@Hypex: welcome! I try to help you coming back to the real Plussy users! :-)
1) Although I supposed, Chine to AU would be cheaper and faster than to Hungary, I see no difference
2) Tha HK page is good, brings up two, one of them is German. (off: I can't help, but for the "Charlotte" company always the Iron Maiden classic come into my mind: "Charlott the h*rlott")
As I see, both needs an offer request by email, I feel much more comfortable to just put the CPU into the basket, pay and forget.
Anyhow, I ordered in the last years more than two dozens of different stuff via Aliexpress, and I've never had any bad experience
(OK, once the cheapo car roof antenna did not perform as well as expected, still looks good)
3) Heatsink: generally speaking copper is slightly better, then alu, but really not a big difference.
(would be nice to apply a heatpipe on 8501 )
On the other hand the grease quality may do a big difference in thermal transfer. In the past after an upgrade I used Thermaltake grease in my PC, but I was unhappy with the result, CPU was very frequently close to upper limit.
Then I bought an Austrian grease, Noctua (you may check their fans too, they are very very silent - for a price). Compared to Thermaltake, with Noctua my CPU showed 8°C less and my GPU 5°C less. Why I mention it? In Hungary the Noctua grease costs less than the half than the upper class Arctic greases, and performance-wise it seems to be very same result.
Thin application of grease is much better than the thick ones.
That's why the preapplied double sided heat transfer tapes frequently fail: they are typically just too thick for the task.
So there are some cheap and good looking heatsinks on the Ebay and Ali with self adhesive tapes (really easy to apply), but with grease they would perform much better. Some Raspberry PI owners reported zero impact on CPU temp when used such a heatsink (even copper ones)
4) Heatsink #2
I think the size of heatsink (bigger radiation surface may help) could be increased into the direction of the memory chips/ROMs
5) 8501R4:
Would be nice. But. I saw a guy offering even 60USD for an 8501R4 chip, but he could not get. I think with a heatsink the 8501R1 will also perform well.
This guy had one R4 in the past, and he offers TED too, maybe worth to ask him:
https://www.ebay.it/sch/commdorec65/m.html?item=181999387743&rt=nc&_trksid=p2047675.l2562
Anyhow, I would be surprised, if all the Aliexpress stock would be R1 only. I suppose it could be a kind of mixed batch.
6) Unfortunately the 8501 is soldered into the MB, not in socket.
So there is a high chance that I will kill the MB, when I try to remove the original IC and try to install a socket. (very bad soldering skills)
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Posted By
Hypex
on 2017-08-19
02:54:37
| Re: Possible 8501 replacement kit?
@MMS
Perhaps I should have posted the a C16 forum where the CPU board would fit?
I don't know if an inverted board would work but there isn't much space. My next suggestion. Stick the CPU in the cartridge slot.
A big thanks for a source of CPUs. It's funny as I started Googling 8502 numbers and came up with some of my own just yesterday. This was after finding a "MOS8501 SemiConductor" listed on eBay by Little Diode, from UK. Perhaps I should have ordered some. I sent a PM asking what it was and they said not available. I rephrased my question and finally got a don't know answer.
I Googled that "string" and something came up. I also tried 251536-01 and it comes up as well. An aircraft spare parts place even has them. LOL. The 8501R1 is a good start. But surely the 8501R4 is the superior choice? Not that it burns out any later.
One find:
https://www.hkinventory.com/p/d/8501.htm
Can't comment on the heat sink but I've been told this combo works. Arctic Alumina Thermal Adhesive and ICK40B sink.
I'd be in your group purchase but I'm outside the EU and in the AU. So it looks like I'm on my own. However, I recently found a Plus/4 owner in my Amiga group. So perhaps I could do a group purchase for the locals here. I've done it before with Amiga software.
:thumbs up:
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Posted By
Imperious
on 2017-08-18
08:08:18
| Re: Possible 8501 replacement kit?
To respond to Hypex's post. I actually tried making up that 6502-8501 board, and couldn't get any response from either the serial or cassette port. I think he removed it from his website due to it not working.
The other one from that Spanish website uses a WDC 65c02 and as that has a BE (bus enable) pin, there is no need to try to recreate that, which means using fewer chips.
Unfortunately He never gave any detailed information on what chips have been used, there is one I cannot figure out what it is. I think he has recreated the Gate-in line which has been ignored on the 6502-8501 schematic.
I have used a G65SC816, 6522, 2x 74HCT688, 74HC245, 74LS04, 74LS74
https://ibb.co/iPhGz5
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Posted By
MMS
on 2017-08-18
08:28:04
| Re: Possible 8501 replacement kit?
As I see the biggest problem: there is not enough free space available within the Plus/4 to close the keyboard if you do not use the original IC.
So even with working converter board, it will be hard to used.
But from the original 8501R1 still some thousand pieces are available, though they are really not cheap.
https://www.aliexpress.com/store/product/MOS-8501R1/1200151_32280168665.html
You should search for 8501R1
Maybe we should add it to the non-existing "important shop" list. ;-D
Still >9900pcs available, that should be more than enough for our scene.
No claims visible, so they seems all in a working condition (more than 20pcs bought in this year, and only positive feedbacks visible)
I have 3 dead Plus/4s, I think 2 of them is most probably due to 8501.
Maybe would be good to make a Group purchase, and spread it locally (within EU).
I would be happy to help in this action, though recently the postage from Hungary to abroad became extreme expensive.
BTW, do you think, it would fit?
https://www.aliexpress.com/item-img/Wholesale-8pcs-set-22x8x5mm-Copper-Heatsink-Heat-Sink-for-DDR-VGA-RAM-Memory-IC-Chipset/32254500983.html?spm=2114.10010108.1000017.2.4b24ae2b7DgMS9
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Posted By
Hypex
on 2017-08-17
00:28:57
| Re: Possible 8501 replacement kit?
Might be a good idea to ask that RobertB. Oh no, YAF. Yet Another Forum.
Since no FPGA 8501 looks like it exists yet I think I found the next best thing. An old project called 6502 to 8501. From 2001! A SpaceTED odyssey.
Here:
http://www.webalice.it/gratteri/65028501.html
It's been tested as working, as claimed here:
http://cbm-hackers.2304266.n4.nabble.com/6502-to-8501-board-IT-WORKS-td4063933.html
But I can see a problem with the design. The 8501 pinout is incorrect. It has P0 to P6 for the port lines. In the schematic it then uses P0 to P6 also. And on the 6522 implementing the parallel port it's wired incorrectly. The top bit is is not connected. The serial won't work despite the effort implementing the logic to do so.
Perhaps if this was corrected and a simpler redesign made if possible this could actually work.
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Posted By
RobertB
on 2017-08-15
20:16:55
| Re: Possible 8501 replacement kit?
Hypex wrote:
> I wonder if...
Those would be questions for CBM engineer Bil Herd at the c128.com forum.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm
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Posted By
Hypex
on 2017-08-10
11:05:30
| Re: Possible 8501 replacement kit?
I wonder if it would have helped if C= used the same layout as the 6510, since it has just one extra port line.
If you look at a 7501/8501 pin layout you will see I/O P5 missing. Which doesn't make sense. Except in putting the clock and data lines at the top in the same position as the C64.
Then in the follow up 8502 P5 is back but P7 is missing! We can't win! It's like C= really stuffed things up for us.
Perhaps if they mapped the serial port to TED or elsewhere it would have helped.
And just to make matters worse reboots like the WDC 6502 are based on the obsolete model and not the popular 6510 with an I/O port.
Perhaps FPGA would be best. Even if it isn't like a real CPU. Or a traditional one.
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Posted By
siz
on 2017-08-10
10:41:25
| Re: Possible 8501 replacement kit?
It runs at the speed and behaves just like the original 7501/8501. The only difference is the port at $00/$01 which is different on the 6510 so the KERNAL had to be patched for it.
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Posted By
Imperious
on 2017-08-10
08:31:28
| Re: Possible 8501 replacement kit?
What speed is the replacement 6510 running at? I thought the 8501 run at 1.76mhz mostly. I do realise it runs 1/2 that speed as well.
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Posted By
siz
on 2017-08-09
15:34:11
| Re: Possible 8501 replacement kit?
To be on-topic: IEC-ATA also did a 6510 replacement for the 7501/8501 with a patched KERNAL for the serial bus port mapping: https://www.youtube.com/watch?v=dfWMJA69g1M
Unfortunately this one (obviously) does not support fast loaders but a 6502/6522 pair could do that. Or an FPGA implementation.
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Posted By
MMS
on 2017-08-09
12:29:19
| Re: Possible 8501 replacement kit?
When I told PLA replacement, I meant the PLA IC in the Plussy that can easily die too.
Certainly for a CPU replacement we need a CPU
PLA replacement project:
http://blog.tynemouthsoftware.co.uk/2015/11/commodore-64-pla-replacements.html
As far as I know the c64 uses exacly the same component.
As I know the top rootcauses of Plus/4 defect (with most frequent causes)
(just guessed figures based on diacussions, threads)
Maybe we can extend this list, how to prevent it, how to be sure it is the defect, and from where you can buy a new or used or alternative component
1) TED maybe 20-25%
Causes: joysticks with autofire, overheating
2) 8501 ~15-20%
Cause: overheating
3) Defective Roms ~20%
Cause overheating
4) defective PLA ~10%
Cause: ?
5) Defective RAMs
Cause: ?
6) with c16: defective PSU
Frequent
Cause: underpowered design, overheating
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Posted By
Hypex
on 2017-08-08
10:11:30
| Re: Possible 8501 replacement kit?
Well I don't mean to steal one from a C128. Even if it is stuck with an inferior 16 colour palette.
There are sources of 8502 CPUs and they tend to be cheaper than 8501s. I don't know if they are any more reliable. It would have been easier if C= used the same pin layout since the 8502 would be a logical follow up to the 8501. From what I can tell one pin side has the same lines but the other side differs, mostly being offset down one set of pins, from an extra pin on top section.
Given the port lines are read internally from location $01 I don't know if they can be set externally. Perhaps a bit of logic involved can detect a read /write on addresses $00/$01 and fill in the missing bits. But I don't know if the memory can be overridden.
It isn't only our machines that have this problem but the C64 as well. Which AFAIK was fairly popular. The CPU lasts longer but 6510 aren't around any more either. Be good if a run could be made of ASIC CPU's to satisfy both markets and any others. I am surprised an FPGA 6510 design isn't out by now that slots in place even if it would be seen as a "fake" CPU.
Given WDC used the 6502 design and bolted things onto it I'm surprised they didn't base it on the 6510 or 8502. It is the closest to being an ASIC 65xx CPU still available. Like above, I don't know if it could be bolted onto a PCB in a DIP 40 pin layout with logic to bring the extra port lines in. Perhaps easier to do if $00/$01 isn't mapped internally but can be set externally.
Another idea I have would be to have some kind of CPU on a cartridge. But I have read the 264 port isn't like the C64 one where it can have an external CPU. Still having a RAM cart would be good. It has been before. And there are cart PCBs available as seen on eBay. Bare and with EPROM.
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Posted By
gerliczer
on 2017-08-08
03:16:57
| Re: Possible 8501 replacement kit?
Cannibalizing working C=128s is a stupid idea. Working 8502s are best to keep as repair material for machines breaking in the future.
WDC 6502s are not compatible, because (AFAIK) they are 65C02s. The so called illegal instructions of the original 6500 derivatives are not present and those also lack the integrated I/O port.
No PLA replacement will ever have even a snowball's chance in hell to be turned into a CPU replacement.
Unfortunately, your best chance is FPGA implementations for [7|8]501 and [7|8]360. It's a pity that nobody is willing to make them.
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Posted By
Hypex
on 2017-08-07
10:40:24
| Re: Possible 8501 replacement kit?
The only concern is the missing port line that is worked around in custom ROM. That said, I wonder if an 8502 converter would be feasible? This has the 7 lines we need and there are sources of 8502 which may be cheaper. But the the odd placement of port bit 5 missing on the 8501 may disrupt this arrangement with bit 5 existing on the 8502 but missing bit 7. So that might be better than a 6510 but still not perfect.
Given that WDC looks like they still produce 6502 derived CPUs maybe it would be best to simply adapt one of those and put it on a compatible PCB. Since it would be a new source. Should be easier than trying to do an FPGA based 8501. Though WDC do provide HDL files.
I have found replacement PLAs here:
http://www.ebay.com.au/itm/C16-4-or-1551-PLA-Commodore-16-plus-4-chip-251641-02-251641-03-equivalent-/191782739112?hash=item2ca7245ca8:g:XJ0AAOSwHnFV03nj
http://www.ebay.com.au/itm/PLA-251641-02-for-Commodore-Plus-4-Commodore-16-and-Commodore-116/182691475391?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
If only one of these could be made up to replace the CPU. Like you said there is a WIP for the TED. The FPGATED.
I have a C16 here that is socketed on CPU but didn't know some Plus/4's has it soldered on board.
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Posted By
MMS
on 2017-08-03
16:55:26
| Re: Possible 8501 replacement kit?
Yeah, it is a fantastic find and development. As fas as I know, next to TED, this is the second most frequent defect (and ceratinly there are RAM, ROM PLA and PSU failures too).
Maybe 15-20% of the dead C16 and Plus/4 could be revived with this? For RAM and ROM we have solutions, for PLA there was a similar project, for PSU there is the c64 ones (for round PSU socket versions), and C16 can work with any unregulated standard external PSU.
So if it really works, only the Plus/4 with square connector, and the TED defect need some further solutions (for the later there is also a nice project too).
(OK I do not say, that desoldering the 8501 and solder a new socket is easy, at least not for me)
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Posted By
Hypex
on 2017-08-02
23:47:28
| Possible 8501 replacement kit?
Hi guys. I came across this just ten minutes ago. Looks promising. An 8501 replacement using a 6510 on a PCB and a replacement ROM. The 8501 data port is not replicated exactly. Would be nice. But in the mean time this could be a goer.
http://hackjunk.com/2017/06/23/commodore-16-plus-4-8501-to-6510-cpu-conversion/#comment-153
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