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| | Previous Messages | Posted By
MMS
on 2021-05-03
14:02:48
 |  Re: World of Commodore 2014 pictures, video, reports
I am far from any HW expert, but for me it seems the BA signal is just an output (an indicator) that you have full access to the data and addresses.
BTW it would have the same meaning as the DMA, just with opposite logic. Instead of pulling the DMA signal like on C64 (and wait 3 cycles after setting it), here the external cartridge may listen to the BA signal and keep the Z80 on hold till TED is not on the border area and not indicating it on the BA line. then you need to wait 3 cycles before writing.
The Z80 has a WAIT line, so the Z80 will suspend the operation (keep in T2 state), so it cannot collide with the TED on the same RAM area.
AEC may work in a similar waay as on C64.
As Jim Brain tols on a forum:
Jim Brain (br...@msen.com) wrote:
": If you REALLY want to read RAM from the internal C64 DRAM, you must disable
: the 6502 inside the 64 and use its cycles for your activities. Hmmmm,
: although I am nowhere near my schematic, you need to look at BE line, and
: as I recall AEC.
: I will go home and check my schematic, but you should be able to discern
: it from the schem. The VIC-II can disable the 6502 when it needs to
: "steal" cycles, so you need to behave as the 6502 does when reading/writing RAM.
: However, your circuit must make sure the 6502 never executes another
: instruction while your circuit is active, because the RAM in the 64 is
: never idle. "
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Posted By
gerliczer
on 2021-05-03
02:04:13
| Re: World of Commodore 2014 pictures, video, reports
and the 8501 CPU's RDY signal also not available on the expansion port.
That is not exactly true. The CPU's RDY input pin is connected to TED's BA output which is also connected to the Expansion Port. The problem is that you should be able to read and drive this signal at the same time to achieve external DMA control in a system compatible way.
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Posted By
MMS
on 2021-05-02
19:53:20
| Re: World of Commodore 2014 pictures, video, reports
I've just run into a project that after replicating the original CP/M Cartridge, now works with 8MHz Z80 CPU, and (more) compatible with the newer C64 models.
According to the schematics, uses the same DMA line as the original one.
And still the original discussion point is, that there is no such line on Plus/4 expansion bus as DMA (NMI not required here), and the 8501 CPU's RDY signal also not available on the expansion port.
The new version:
https://www.pcbway.com/project/shareproject/8MHz_Z80_Card_for_Commodore_C64.html
The original CP/M replica project:
https://www.pcbway.com/project/shareproject/Commodore_CP_M_Cartridge.html
The schematics of the new:
https://github.com/DL2DW/Z80-Card_for_Commodore_C64/blob/main/Schematic/Z80%20Card%20for%20Commodore%20C64%20V0.3.PDF
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Posted By
SVS
on 2015-01-08
02:06:33
 | Re: World of Commodore 2014 pictures, video, reports
Made by SGS.
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Posted By
MMS
on 2015-01-06
14:51:28
| Re: World of Commodore 2014 pictures, video, reports
SGS or Olivetti? BTW nowadays you can find only "made in China" or "made in Taiwan" ones 
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Posted By
SVS
on 2015-01-06
14:06:11
| Re: World of Commodore 2014 pictures, video, reports
The card of the image is for C64. One of my friends had the C64 at time and even if this large-sized cartridge is here in my treasure collection I don't remember if it's mine or its. Anyway I'm sure he owned the CP/M disk for C64 with the cartridge!
BTW did you noticed the Z80 with the "made in Italy" write?
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Posted By
MMS
on 2015-01-06
06:56:23
| Re: World of Commodore 2014 pictures, video, reports
I think it was SVS who told that such card is not possible with plussy due to missing 'cpu halt' line. So it should be the c64's z80 card. It seems to be rather limited, as was compatible with c64 up to 1983, as i know.
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Posted By
Litwr
on 2015-01-06
09:52:38
| Re: World of Commodore 2014 pictures, video, reports
C128 is the biggest success of any CP/M comaptible machine
IMHO C128 success was caused by other reasons. z80 and cp/m in it is like the fifth wheel at the coach. The most successful cp/m machine is Amstrad PCW series. I've read that they still used somewhere. I worked with PCW 8256/9512 - they are true CP/M machines and good text processors. Only the printer with 8256 was a bit odd.
VIC-2 can't be used for 80 columns screen that makes it useless for cp/m. VDC is very powerful thing, it may use up to 64 kb video RAM and it doesn't need badlines - c128 vdc demo.
14 cycles, resulting ~142KB/sec copy speed
there is an obvious error, there are 13-14 cycles and 72-78 KB/s. So in this case z80 is faster. However 6502 1MHz overall performance is close to 2.4 Mhz z80 without wait states.
CPC with 4MHz+128K is faster
it is much faster and better for cp/m... But PCW is the best CP/M machine.
the big transport company
if they used CP/M only then it was the waste of money and ineffective (slow) work.
SVS, could you provide more details for the presented card? Is it for +4?
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Posted By
MMS
on 2015-01-05
15:04:00
| Re: World of Commodore 2014 pictures, video, reports
Z80 has no access to SID or VIC: like the Spectrum
Still, C128 is the biggest success of any CP/M comaptible machine, sold 4 millions, despite high price.
Well, if CP/M dos65 would be available at that time, no need for Z80 in c128, would increase competitiveness on the market.
(less complicated architecture --> cheaper machine --> more sales --> bigger profit)
CP/M could also run way faster (2Mhz 8502 + VIC II).
But there are interesting limitations, seems to copy some Plus/4 weirdness.
8502 clocked down to 0.98Mhz and several badlines... You can run faster only if VDC enabled, but very hard to program, no BASIC commands at all, and for a long time no documentations at all...
BTW Z80 has no access to VIC, but has no bad lines too! So can have 2 times the memory access than 8502 in the same machine. BUT, to match to the memory speed, Z80 is said clocked down to 2MHz.
BTW there is a guy (seems reflecting on your speed comment) that 6502 is faster on 1MHz than the Z80 at 2 Mhz "LDIR/LDDR on Z80 take 21 cycles/byte, soy you can theoretically move ~95KB/second at 2MHz. LDA,X+STA,X+INX+BNE takes 14 cycles, resulting ~142KB/sec copy speed. With reasonable unrolling 8502 is faster even at 1MHz."
Memory is also an issue. Experts says CP/M bare minimum requirement is 32K, but probably OK with 48K.
CPC had 128K access. As I see, the Z80 in C128 can see one dedicated bank. tTat means 64k.
So it is not a big surprise, why a CPC with 4MHz+128K is faster than a 2Mhz Z80 + 64K in C128.
Too bad that C128 was more expensive. But still, there were some professional use for it's CP/M.
I do remember the big transport company my mother worked, used C128s to manage tarnsport records, in CP/M mode and some database program (first I was impressed, as from 3 meters it looked like an Amiga )
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Posted By
SVS
on 2015-01-05
14:48:46
| Re: World of Commodore 2014 pictures, video, reports
And what do you think about this ?
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Posted By
Litwr
on 2015-01-06
00:01:30
| Re: World of Commodore 2014 pictures, video, reports
Hi, MMS! Thank for you the link to dos65 - it is about my idea. More work and more programs will be transferred from z80 to 6502. However a man can do very much only theoretically...  BTW the biggest problem is the screen size. A lot of good cp/m programs use 80x24 screen. IMHO z80 is the ugliest CPU ever known. Yes it works, has several good instructions but its success shows that our world is often wrong.
SVS, z80 emulator will be very very slow. The better way is to write a binary translator from z80 to 6502 but this is very big task and I almost sure that 6502:z80 speed ratio will be below 1.5:1 - this is slow. IMHO only the manual binary translation may give up to 3:1 ratio. However i8080/z80 programs are small in size so it is doable.
IMHO C128 z80 is nonsense because 6502 at 2 MHz and 80 columns screen is at least 2.5 times faster. C128 was relatively expensive but its cp/m is 2 times slower than at cheaper Amstrad CPC/PCW. z80 has no access to SID or VIC.
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Posted By
SVS
on 2015-01-05
02:53:21
| Re: World of Commodore 2014 pictures, video, reports
A solution (I had thought in the years) could be to write a ML Z80 emulator. I had started the project but not continued.
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Posted By
MMS
on 2015-01-04
14:49:52
| Re: World of Commodore 2014 pictures, video, reports
Gerliczer,
for me it is both OK
but the Internet stream is not a good analogue, as the internet data stream goes though a motherboard IC managing the internet protocol, then goes to the CPU, then to VGA card (GPU), so the internet datastream does not directly goes onto your screen (but would be great). CPU is surely involved, as the antivirus SW is checking the data goes though the processor, and it is the only way can control it. Or as I think...
But anyhow, no need to agree with me, or I can agree on that DMA matter. Makes no difference, it is a hobby discussion forum for fun :-)
Litwr,
I know your programming skills, but how can be realized without the source code from Digital Research?
On the other hand, you seems not the first who has this idea
The link below may save you some dozens of hours of programmers work, as it contains the CPM/65 C64 runnable d64 versions with several documentation and as I see, ever source-code.
If you are lucky, it mostly uses standard Kernal routines (=Plus/4 is same with C64), so only the PRG start address, and the memory mapping need to be changed (character map, screen and color map, color registres, etc). I do not know, how deep the CP/M usually goes.
Though i did not read the documentation... But a really good start
http://www.z80.eu/dos65.html
Supposely the 6502 based CP/M programs for C128 are somehow useable, but the memory limitations may cause some troubles.
And you also need an 1571 drive, if you do not own any yet. (but nowadays not so expensive)
Some sources:
C128 & 1571 CP/M documentation:
http://www.herne.com/cpm.htm
some more C128 info:
https://sites.google.com/site/h2obsession/CBM/C128/cp-m
CP/M GFX library and the link to the HiTech C Compiler 3.09
http://www.z80.eu/gsx.html
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Posted By
gerliczer
on 2015-01-04
05:54:08
| Re: World of Commodore 2014 pictures, video, reports
@MMS: People thinking that not using the NMI line in Z80 cartridge for the C64 makes it slow are idiots. Even I, who don't really have any proper hardware knowledge, know that the very different system design philosophies of 65XX and Z80 systems cause the limited performance.
For the DMA, I think we are splitting hairs over words, but to me if the system, as in either TED of the CPU, has no direct control over what arbitrary data will be transferred to which arbitrary address in what arbitrary amount then it is not true DMA transfer. Given your definition, we may even surmise that watching let's say a party live stream over the Internet is a DMA transfer (over the Internet). But please point me out where I'm mistaken.
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Posted By
Litwr
on 2015-01-04
01:34:06
| Re: World of Commodore 2014 pictures, video, reports
My researches show that 6502 of C+4 is the speed equivalent to 3.4 MHz z80. So z80 cartridge is not the necessity to run CP/M. The several dozen hours of programmer's work may create CP/M for 6502. This software solution will be much faster than z80 cartridge.
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Posted By
MMS
on 2015-01-03
18:08:15
| Re: World of Commodore 2014 pictures, video, reports
OK, a little OFF:
you are probably right: the RDY and AEC inputs used by the existing Z80 cartridge, and NMI not, though some people think that's why the z80 cartridge was a flop (and too slow). AEC input we also have, but we seems do not have the ReaDY pin on the extension port. (So you cannot command to halt the processor temporarily).
So I was wrong with NMI.
DMA: if you see a memory address just with the gfx data, and it is directly loaded from an external device, for me it is a direct access.
They did not use any Plus/4 routine or CPU for the memory loading, but accessing and writing it directly.
OK, not the same or as flexible as the Intel's DMA, but rather similar, if you think twice.
Maybe closest to the "cycle stealing" DMA method, as the CPU should wait with the "ROM" reading till the external device stopped the writing of the "ROM".
"A DMA közvetlen adatátvitelt eredményez a memória és az I/O készülék között, a CPU igénybevétele nélkül. Igy a periferia közvetlen memória-hozzáféréssel rendelkezik."
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Posted By
gerliczer
on 2015-01-03
16:44:19
| Re: World of Commodore 2014 pictures, video, reports
You are wrong with NMI and DMA MMS. NMI is not needed at all for interfacing an external CPU. The capability to disable the internal CPU is needed. The Evo Lution wild demo hardware did not use any kind of DMA. It was using the existing capability to use external ROMs in the system.
MMS, tévedésben vagy az NMI és DMA kapcsán. Nem maszkolható megszakításra nincs szükség külső processzor illesztéséhez. Ahhoz az kell, hogy ki lehessen kapcsolni a beépített processzort (az más kérdés, hogy a 64-esben ezt valószínűleg a DMA abuzálásával csinálják). Az Evo Lution wild demo hardver nem használt semmiféle közvetlen memória elérést. A rendszer már létező külső ROM használat képességét használta (valószínűleg belapozott a Plus/4 felső címtartományába valamilyen memóriát, amit a gép processzora ROM-ként látott, és a gépben futó program az ebben a "csak olvasható memóriában" tárolt grafikus adatokat jelenítette meg).
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Posted By
MMS
on 2015-01-03
15:02:45
| Re: World of Commodore 2014 pictures, video, reports
there was CP/M for C128, and a Z80 cartridge for C64 with a reduced cp/m, but Z80 was a must in all cases. As i learned, there is no NMI in our Cpu, so such a cartridge will never ever be produced for plussy.
(Although the same i though about DMA loading, and it was done this year.)
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Posted By
Chronos
on 2015-01-02
15:13:39
 | Re: World of Commodore 2014 pictures, video, reports
great! thanx for posting!
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Posted By
Litwr
on 2015-01-02
14:52:52
| Re: World of Commodore 2014 pictures, video, reports
A z80 board... It is too plain. I hoped to find a hidden CP/M variant. CP/M is i8080 based and very small and easy so an enthusiast might convert it to powerful 6809 or even 6502. BTW thank you for information.
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Posted By
Litwr
on 2015-01-02
01:55:19
| Re: World of Commodore 2014 pictures, video, reports
CP/M at SuperPET9000? How is it possible? CP/M works with i8080, i8088... Is there CP/M for 6502 or 6809?
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