1024kb memory upgrade for Yamaha MSX2 YIS503

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By Alexey

Guardian (2382)

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19-05-2015, 00:44

Just assembled 2 boards with 1024kb memory upgrade for Yamaha MSX2 YIS503. Boards are designed by Kamil Karimov (caro). All chips have SOP form factor, very easy to assemble. I have 7 more boards + parts for assembling 2 boards. If anyone is interested, please contact me. The boards are compatible only with YIS503 model of Yamaha MSX2.

Alexey

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By gdx

Prophet (3034)

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19-05-2015, 02:32

Some YIS-503II & YIS-503III users will be happy.

Is it supports reading of ports?

By Alexey

Guardian (2382)

Alexey's picture

19-05-2015, 10:49

Not sure what you mean by "reading of ports". It passes all tests with TestRAM and TestMAP utilities. Games work, just tried it with a disk version of Metal Gear 2 and some other games.

Alexey

By alexito

Hero (555)

alexito's picture

19-05-2015, 16:32

Hi Alexey.
i want to buy 2 boards of those.Already sent PM to your Email

By Alexey

Guardian (2382)

Alexey's picture

19-05-2015, 18:10

@Alex: I replied to you. Smile

By Grauw

Ascended (8451)

Grauw's picture

19-05-2015, 22:52

I have a Yamaha CX5MII, does this board also work with that? In that case, I’m very interested in a board + parts set.

Pics of the RAM module in the CX5MII: 1 2 3 Service manual.

Also, on a similar topic, any chance of a VRAM module upgrade?

p.s. gdx means mapper readback. If you type print inp(&hfe), does it print 255 or another value.

By Alexey

Guardian (2382)

Alexey's picture

20-05-2015, 12:03

If the pinout of the RAM board connector is the same, then there's a big chance that it might work. The CX5M-II is MSX2 and is quite similar to YIS503III that this module was made for. But I can't download the service manual for CX5M to compare the pinouts.

As for the VRAM upgrade, there was some idea to solder extra chips on top of the existing ones while not connecting certain pins. I also see that the 8 placeholders (for VRAM chips?) on the CX5M-II board (to the left of VDP) are empty. Maybe if 4 or 8 memory chips (4164) are installed there, this will work as 128/256kb of VRAM. This is just a theory, I am not a professional electronics engineer.

Alexey

By gdx

Prophet (3034)

gdx's picture

20-05-2015, 15:33

This connector seems to be the same on the CX7M-128 and probably the CX7-128 also.

http://hanihanisayoko.seesaa.net/article/411897487.html

but the CX5M-II/128 below seems not to have this connector:

http://www.cx5m.net/cx5m-ii128-msx2-conversion/

:-?

By Grauw

Ascended (8451)

Grauw's picture

20-05-2015, 18:43

My CX5MII’s motherboard is the same as the one in that CX7M/128 picture, see the serial number printed on the board. It’s not like the one (XB300) in your second link. I think they changed boards for later revisions.

Better service manual link: http://www.grauw.nl/etc/msx/cx5m/yamahacx5msm.pdf

Alexey: Yeah there’s room for VRAM chips on the board indeed, also there is unused space for an RTC on the board, but if it’s a simple expansion module it would be easier and I wouldn’t have to modify the machine.

By Alexey

Guardian (2382)

Alexey's picture

20-05-2015, 22:34

The "print inp(&hfe)" command returns 193. Most of games and software work fine, tests with TestMAP and TestRAM pass. Some megarom games with Russian loaders don't work, but this is normal as the loaders assume certain memory configuration on Russian MSXs.

Sorry, I can't really recommend anything concerning the expansion of VRAM. I have no knowledge of this kind. You might want to approach someone with a better hardware knowledge: Bas or Nyyrikki.

Alexey

By Grauw

Ascended (8451)

Grauw's picture

20-05-2015, 23:28

I compared the service manual of the YIS503II/III to the CX5MII, the pinout of the connector is the same.

So yeah I’d like to buy a board + parts set, I’ll send you a mail Smile.

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