Using SaRuMan-64 in an MSX

By Caliostro

Expert (86)

Caliostro's picture

21-02-2022, 18:36

Hi everyone, a very simple question, surfing the internet looking for components for the commodore 64, I found the SaRuMan-64 module, my question is: can I use this component to replace the ram of msx and msx2?

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By jltursan

Prophet (2619)

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21-02-2022, 20:32

If you find a MSX model with 2 x 64KBx4 DRAM with the same spacing as this little PCB, the answer is yes.

By Caliostro

Expert (86)

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21-02-2022, 23:42

for the same spacing is not a problem, I only care if it is compatible, I had seen modern chips used for the VDP, but I had not seen modern chips used for the ram, this gives me a new idea for a portable MSX project

By CASDuino

Champion (298)

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22-02-2022, 00:01

I doubt it.

Rather than looking at the SaRuMan-64 your should look at the data sheet of the CY62128ELL-45SXI and see if that could be compatible with the MSX Banking as it is a 1Mbit (128k x8) Static RAM. I don't think one module would do it because of all the different makes and then there would be compatibility issues but if you're designing your own hardware MSX then it might be more likely.

By Caliostro

Expert (86)

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22-02-2022, 08:10

i'm not very good with electronics, but i built a 64k cart that uses the IS62C1024AL and it works fine, isn't it the same?

By jltursan

Prophet (2619)

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22-02-2022, 08:24

If you're thinking in using it as VRAM, I remember that someone found some not obvious issues using SRAM as replacement; so beware.

By Caliostro

Expert (86)

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22-02-2022, 13:10

omega uses modern memory for VRAM, I don't remember having any problems

By jltursan

Prophet (2619)

jltursan's picture

22-02-2022, 13:58

You're right, IIRC it was related to the MSX1 VDP, not Yamaha ones.

Worth trying then.

By gdx

Enlighted (5705)

gdx's picture

23-02-2022, 12:37

I think SaRuMan-64 has 128 kB because it has a mapper C128 compatible.

CY62128ELL-45SXI chip is the SRAM. It is easier to address than DRAM.
The little chip is to manage the mapper and the 3-pin chip is to convert 5V to 3.3V because chips are powered at 3.3V.

SaRuMan-64 probably can't be used on MSX because of the mapper.

By Caliostro

Expert (86)

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23-02-2022, 14:18

This is really bad news ... but why include a mapper? SaRuMan-64 is a replacement card for the 2 DRAM chips, so as not to increase the memory

By gdx

Enlighted (5705)

gdx's picture

24-02-2022, 01:00

It's just an assumption. The small chip may be there to simulate 4-bit DRAMs. And in this case, the size of the SRAM would be 128kB to put the low 4bits on 64kB and the high 4bits on the other 64kB, or it's just a question of price. 128kB is easier to find and cheaper. In this case, 64kB is unused.
The first solution seems the best to me. It's a bit like putting a Memory Mapper on MSX1.