[GEM Development] FreeGEM drivers updated

[John Elliott]

> Now that sounds rather peculiar, indeed; how do they/does the hardware cope
> if you have bits set in several planes?  Presumably it's not actually a
> 16-colour mode in disguise; I guess the card assigns priorities to the
> planes or something?

  A 1024x768x4 (or 768x1024x4) mode needs 192k of video RAM. The 4-colour
drivers map it as 4 x 48k planes:

 - Red even columns
 - Red odd columns
 - Green even columns
 - Green odd columns

  So there are only two planes 'under' any given pixel. It also means, I 
think, that half the bytes in any 4-plane MFDB will be unused.

-- 
John Elliott