Oh, an interesting project. So this is an external GFX card for the CPC? What are the advantages? Isn't it quite slow to send all GFX data to the card via OUT commands instead to write into V-RAM?
From my limited MSX2 coding...
Yes,just writing data to the GPU is slower, but even in bitmap mode it allows you to copy all your 'sprite' data to spare gpu ram before the game loop, then send commands like 'copy this memory to this position' and it's effectively like multithreading, the GPU just gets on with it, and you can do other stuff.
I believe the 9990 has some pretty decent tiling and sprite code too, so it will be more like coding a console than the bitmapped system we're used to.
As the MSX2 has the same sound chip and 64k base ram like the CPC, this should encourage ports of the newer MSX games to the CPC... unfortunately, however, as the MSX3 that this was intended for was never completed, it's my understanding that the 9990 is not backwards compatible with the MSX2/+ GPU... so it will not enable easy porting of MSX2 games...
please correct me if I'm wrong!