32k or 64k RAM upgrades.

By CASDuino

Master (165)

CASDuino's picture

11-03-2020, 05:21

A friend of mine has two 32k MSX. a Yamaha CX5M and a Pioneer PX7.
He would like to expand them to 64k so he can get the most put of them but for smallest bucks.
Are there any gerbers or schematics for smaller RAM carts or expansions?

I know he could get a Carnivore etc but they are expensive and not what he wants.

I also know the Yamaha is more tricky than most due to its hardware so a universal RAM expansion would number preferred if possible.

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By Jipe

Paragon (1404)

Jipe's picture

11-03-2020, 08:52

By gdx

Prophet (3829)

gdx's picture

11-03-2020, 09:21

The SD-512 is not very expensive. About €60 for 512kB RAM + 2 SD slots + Mextor (and gold plated contacts).

By st1mpy

Hero (562)

st1mpy's picture

11-03-2020, 22:45

Is there any advantage/reason for someone to get just a 32k/64k upgrade rather than a mapper on msx1? Assuming that mapper is recognized as a memory upgrade.

I've recently built a 128k mapper, and it seems to expand the px7 to 64k atleast as I was able to use dos on floppy and beer ide. So I didn't bother making a 64k ram cartridge. I suppose a 64k ram cart is cheaper to make slightly.

By Manuel

Ascended (17075)

Manuel's picture

11-03-2020, 23:10

The mapper should be MSX1 compatible, i.e. it should initialize by itself to not have all the pages map to bank 0... but in a nice linear order, so that a full 64kB shows up in the slot of the mapper. And whether it is actually used as a mapper is then even optional. Normal MSX Memory Mappers do not have such initialization, so the ROM is doing it. And that code is not in the ROM of a normal MSX1.

By gdx

Prophet (3829)

gdx's picture

12-03-2020, 01:07

Yamaha CX5M and Pioneer PX7 have 32K RAM in slot 0. So with a 64K expansion many software will not run because the RAM is divided into two slots at start. MSX-DOS1 will be auto-bootable and will run fine.

With a memory mapper the MSX-DOS1 is not auto-bootable and all software that need more than 32K can not run directly except if it is a mapper that initializes itself its segments.

When the mapper can't initialize its segments you have to entered OUT&HFD,1:OUT&HFC,0 at each start to be able to run the DOS or 64K software but there is also another more effective way for 64K software and more, this is BMMS.


BMMS is also useful even if the mapper initializes its segments to avoid the RAM divided into two slots.