@blacktiger: yes you're right, i did some tests, and i can refresh 5 sprites (arcade sized) without any optimisations, and with a sprites animation @30fps,and it uses 50% of CPU cycles .
But if MD has all the arcade patterns (however i doubt), it's impossible to fit 500 ko/caracters without any very good compression,even with AC ..
The Sega-CD port of Final Fight isn't very good overall for the hardware and is very far off from the arcade. It just happened to be the best console port until the Capcom Collections.
And i doubt heavily that capcom was able to fit all arcade animations in 768 ko of cache .
No, but if the data is in a spare area of VRAM, it can be dma'd to where it needs to be quickly. Which allows you to use the rest of the frame to refill the transfer area....
There are too many datas, and of course you need to have a cache in vram of each caracter.
in my tests 50% is for a transfer of half size of data/ frame for a 30fps anim.
Why must it be compressed? The Arcade card has more memory than the system 3.0 card (iirc). In any case, can't it be loaded into adpcm memory and sent from there? (64K adpcm memory + direct to vram writing from adpcm.... maybe not dma speed, but very close, I'd bet.)
Honestly, pushing 3K of data per frame sounds doable to me....
In fact the problem is not transfer, is doable,it's all sprites patterns .
For exemple,the sprite sheet of axel, his size in arcade version is about 500 ko ..
For main caracters (cody,guy haggar), is 3x larger, stef told me that md version has all the coin op animations ...