Max memory 576k

[zhulien]

hi


I am wondering why the wiki page states maximum ram of cpc to be 576kb given recent commercially available products are up to 512kb more... if restricting to commercially available products that is. But then you can add another 24kb onto that if you include vidi and multiface 2 as well.


Julian

[arnoldemu]

I am wondering why the wiki page states maximum ram of cpc to be 576kb given recent commercially available products are up to 512kb more... if restricting to commercially available products that is. But then you can add another 24kb onto that if you include vidi and multiface 2 as well.

good point and the wiki can be changed.

I guess it depends on the point of view.

What the hardware can support vs what is usefully used by software.

Technically the cpc could support almost any amount of ram - it depends on the method to access it.

576KB is the max which is fully dk'tronics/amstrad/dobbertin. (it uses all 8 bits of the data written to port 7fxx and the port is decoded in the normal way).

Dk'tronics/amstrad/dobbertin is the most widely used memory type and the most supported (many games and programs support it), but it's sad that it's mostly 128KB that is supported - although that is changing.

True the vidi and multiface 2 have extra ram, but it's not dk'tronics compatible is it? And it's much less widely supported? Not all of the multiface 2 RAM can be used because there are a few bytes (6 or so) that are updated when specific I/O writes are done. I don't know the details of the vidi.

I have a CPC464 with Vortex 512KB Ram expansion and I think 3 programs support it. (Vortex's modified CPM, Discology Disc copier and Vortex's BOS rom). So in this respect I do have 576KB RAM but I can't use it for much.

Contrast this to the X-MEM, I have 576KB ram and 512KB rom and the majority of software can use most of it with some using all of it.

The other expansions (1mb, 2mb, 4mb etc) are extensions to the dk'tronics/amstrad/dobbertin method, and because of i/o port decoding then they are not 100% compatible.

[arnoldemu]

hi


I am wondering why the wiki page states maximum ram of cpc to be 576kb given recent commercially available products are up to 512kb more... if restricting to commercially available products that is. But then you can add another 24kb onto that if you include vidi and multiface 2 as well.


Julian

I have been looking on the wiki, can you paste the URL of the pages that state a max of 576KB Ram here please?

EDIT: Found one place, it was mostly copied from wikipedia and i have updated it. Wikipedia states:

"MemoryAmstrad CPCs are equipped with either 64 (CPC464, CPC664, 464plus, GX4000) or 128 (CPC6128, 6128plus) KB of RAM.^[20][22] This base memory can be extended by up to 512 KB using memory expansions sold by third-party manufacturers, and by up to 4096 KB using experimental methods developed by hardware enthusiasts. Because the Z80 processor is only able to directly address 64 KB of memory, additional memory from the 128 KB models and memory expansions is made available using bank switching."

Which is fine.

[Sykobee (Briggsy)]

It's right that when adding an expansion the extra 64KB in the 6128 is disabled?


I suspect the standard for 4MB expansions has been set now, as there's only one that I'm aware of :-)
But for most software that makes use of more than 128KB, I think 576KB is a good target.

[zhulien]

I am guessing a lot of people got an X-Mem from toto, and the Y-mem also from toto gave it yet another 512kb RAM and 512kb ROM.  Symbos uses 1mb RAM, not sure though if it is X-Mem+Y-Mem yet as I have not yet tested the latest release.

[roudoudou]

but it's sad that it's mostly 128KB that is supported - although that is changing.

You mean 64K max with spanish products?

[GUNHED]

hi


I am wondering why the wiki page states maximum ram of cpc to be 576kb given recent commercially available products are up to 512kb more... if restricting to commercially available products that is. But then you can add another 24kb onto that if you include vidi and multiface 2 as well.


Julian

There are 0.5; 1.0; 2.0 and 4.0 MB RAM expansions. The known maximum (as far as I know) is 4 MB. I heart of 8 MB, but don't know somebody having one.

[PulkoMandy]

The first expansion to do more than 512K was the MEMCARD from RAM7. This is where the trick to use address bits for extra pages of RAM was used.


As for disabling the internal expansion RAM of the CPC, it depends on the extension you plug. DkTronics one of 128 or 256K will properly decode all bits, so if you try to access the first 128 or 256K of RAM, you get the one from the expansion, and after that, you get the one from the CPC. However if the expansion is 512K, there is no space for the extra internal 64K to show. Unless you have another way to disable the external extension (which would again be non-standard).

[CraigsBar]

Is anyone currently making 1mb and above cards for sale. I'd love a 1, 2 or 4mb cpc but cannot seem to find a source for such a card.

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[zhulien]

Is anyone currently making 1mb and above cards for sale. I'd love a 1, 2 or 4mb cpc but cannot seem to find a source for such a card.

I am hoping to prove my 512mb CPC RAM expansion soon.  Yes, it is a lot of banks.

[CraigsBar]

I am hoping to prove my 512mb CPC RAM expansion soon.  Yes, it is a lot of banks.

Hahaha, that really pushes the limits lol.

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[Shining]

Is anyone currently making 1mb and above cards for sale. I'd love a 1, 2 or 4mb cpc but cannot seem to find a source for such a card.

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Ask TOTO for an Y-MEM. By using x+y-mem you have an 1mb expansion.

[CraigsBar]

I want to remove my xmem. And have a single board that is only a ram expansion.

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[CraigsBar]

The rom part of the xmem is disabled anyway

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