Posted By
Spektro
on 2018-10-10
05:13:42
 |  Photo of an unknown 64kB memory expansion
Quality photo of an unknown 64kB memory expansion. It looks similar to the Pagesetter cartridge: http://plus4world.powweb.com/hardware/Pagesetter_Cartridge
It's printed on the cartridge's circuit board:
64kB-SRAM-CARD (C) 1993 SYNERGY
Idea, Design: Christian Schäffner
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Posted By
MMS
on 2018-10-10
11:22:26
 | Re: Photo of an unknown 64kB memory expansion
Well, definitely it could work. But it is SRam. I know there is no waitstages, can it work as a normal Ram?
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Posted By
siz
on 2018-10-10
15:08:56
| Re: Photo of an unknown 64kB memory expansion
No. This one works as an EPROM card emulator and has a battery to power the SRAMs to keep data while the plus/4 is not turned on.
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Posted By
Spektro
on 2018-10-20
05:03:02
| Re: Photo of an unknown 64kB memory expansion
I tried the cartridge on my C16 and it reported no extra memory: on the start screen it still said 12277 bytes free when the card was plugged in. I don't know what the cartridge switches are for. I tried every switch combination and reseted the machine on every switch change, but Basic kept reporting the same amount of memory: 12277 B.
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Posted By
gerliczer
on 2018-10-20
05:50:51
| Re: Photo of an unknown 64kB memory expansion
You misunderstood it Spektro. Although siz wrote (S)RAM, this is not a memory expansion card, but something like the Jack Attack game cartridge. It can be used to add custom ROM content to the system. A bit like the EasyFlash for the C64. It is made of RAM for the purpose of changing its content at will. It's useful to develop cartridges for the TED machines. One of those switches turn on and off write protection. The others change different configuration aspects. You should look up Solder's stuff, maybe there's some information about this puppy. His name is etched onto the component side of PCB, so its his creation.
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Posted By
MMS
on 2018-10-20
15:32:55
| Re: Photo of an unknown 64kB memory expansion
I highly suppose that the mentioned information on Solder website is not correct, or at least for this one.
Because then the cartridge should have C64 connector, and not 50pin as we see.
As on the picture I see 25 pins, it should be compatible directly to the Plus/4 port.
Why the expansion-port-splitter?
Because you cannot get such a 50pin connector the Plus/4 requires for a splitter. (and built into the machine)
So, you want to build a splitter, but cannot get the 3 connectors required for the card.
Solution: if both the future cartridges (plus/4 ones!), and the splitter should operate with the C64 connector, it is a working workaroundt, though you cannot connect it directly to the Plus/4 port.
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Posted By
SVS
on 2018-10-21
07:25:19
 | Re: Photo of an unknown 64kB memory expansion
And don't forget to use the modified operating system Roms (OS92 or OS96) instead of standard ones.
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Posted By
MCes
on 2019-11-02
13:50:43
 | Re: Photo of an unknown 64kB memory expansion
@MMS
The linked one can't properly work on an unmodified C16.
Maybe that we have to reverse a concept to understand the situation:
An not modified C16 can't work with any external memory expansion.
It's not a problem of how the expansion is designed, the problem is how the C16 is designed.
Another pair of shoes is to filling of RAM (paged?) the cartridge external memory areas,this solution increase memory but it can't be managed as a native 64k memory bank
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Posted By
siz
on 2019-11-03
03:43:18
| Re: Photo of an unknown 64kB memory expansion
I'm really curious why do you think it does not work? I have a similar expansion which I've used in my C116 (perhaps in one of my C16s too) and worked perfectly.
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Posted By
MCes
on 2019-11-03
05:48:18
| Re: Photo of an unknown 64kB memory expansion
@SIZ
Into a unmodified C16 each RAM access cycle (64k, via /CAS signal) will active the internal 16k ram bank (with its base or mirror address) and the 16k bank will occupy ALWAYS the bus: if an external cartirdge will try to occupy the bus durind a RAM access it will be ALWAYS in conflict with the internal ram bank.
A different concept is the cartridge on the first post of the thread: if I understood well it cover the cartridge external ROM space with paged RAM, it can be done but it isn't an expansion of the internal bank RAM from 16k to 64k (also if it contain 64k of paged accessible RAM)
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Posted By
gerliczer
on 2019-11-03
07:02:26
| Re: Photo of an unknown 64kB memory expansion
There are photos of naked 64kB Memory Expansions in the Hardware section. Those that are sharp enough to read the marking of the components always have a pair of 74LS257s. You are the expert, tell me please the following. Why are those there? And what happens when they are operating?
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Posted By
siz
on 2019-11-03
08:51:47
| Re: Photo of an unknown 64kB memory expansion
I agree with you on the bus conflict but I tried it myself: it's working. It couldn't have been marketed if it's not. I never tried to understand how it works tho.
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Posted By
MCes
on 2019-11-04
10:08:08
| Re: Photo of an unknown 64kB memory expansion
A cart is not sufficient to define its work: on the instruction manual you can find which traces has to be cutted....
example:have a look at the last pic.... you have to cut the pins9 of your ram chips...
64K-RAM Speichererweiterung
I'm suspecting that the only cart that could work (improperly) are the cart that has a transistor on it because the /CAS signal could be overloaded to Vcc (so it remain in H state = not RAM access) but this overcurrent can be sensed by B-E junction of a PNP transistors that can used to sense the /CAS signal for driving the cartridge RAM without bus conflict....
This method can work, but the TED /CAS line will be overloaded and it couldn't be a great idea for the TED health...
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Posted By
MMS
on 2020-06-07
05:47:31
| Re: Photo of an unknown 64kB memory expansion
Just to add a copied sentence from an expert Viktor Tóth who wrote the "C16's internal structure" book.
On his homepage he wrote:
"Or maybe I can repeat the accomplishment of my sadly deceased friend, Ferenc Szatmári: for a machine specifically designed to NOT permit the construction of a memory extension cartridge (in order not to compete with other Commodore models) Feri managed to design one anyway, a cartridge that successfully tricked the C-16's control bus into accepting external memory as a substitute for its internal RAM." (MMS comment: certainly he speaks about C16  )
He was involved in different interesting projects, just about Commodore:
"http://www.vttoth.com/CMS/projects/169-commodore-64-game-development"
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