VRAM board for Yamaha CX5MII

Pics can't be seen, browser says "forbidden".

So was CAS0 or CAS1 originally connected to the expansion board? Because this matters for the text I will put for the airwire connector. Is there a way to easily connect a wire to CAS pins of the VDP?

Ok, here's the board with 4 4464 chips (128kb) and a pad to solder the airwire to CAS 0/1 of the VDP. If the board's CAS connector is routed to VDP's CAS0, then the airwire must be connected to CAS1 and vice versa.

I am not going to produce these boards myself unless I have at least 5 orders. Otherwise I can't even cover the expenses of making those boards. I am going to order my other boards soon, so if you need this VRAM board for your CX5MII MSX, please contact me ASAP.

If you want to produce these boards yourself, I can share the schematics and Gerber files. The only thing I will ask in return is 1 of these boards. I think it's fair enough.

Humm, originally the board was indeed designed to have the 1st bank of 64KB onboard and the 2nd bank 64KB on the expansion.

In the wild you probably will find both possibilities: boards with CAS1 and others modded in-factory to have CAS0 on the VRAM expansion connector.

AFAIK, that won't change your expansion board design. The only difference will be that, when installing the board, the owner will have to connect the wire to the unused CAS accordingly.

That’s the next step . As I mentioned earlier, the BIOS ROMs are socketed, one of which is a “sub-rom” (contains mode 80 support), so I hope it’ll be easy to modify.

But for now, some (European) software will probably bypass the BIOS and already work, and I can also try it out with my personal projects.

Yes, I checked the pics of YIS503II board and it indeed is very similar to CX5MII. So I am pretty sure the board will work there. Thanks for the hint!