faheyr@silver.ucs.indiana.edu (Bob Fahey) (09/06/90)
Hi there. I am writing a utility in Assembly, and am coming across an unknown
problem. I need to be able to display 16 colors (i.e. 4 bit-planes, 640x200).
When I have the copper set at 3 b-planes, everything works great, but when I
switch to 4 b-planes, everything S-L-O-W-S way down.
Is this a hardware problem? It seems that when I read the keyboard, and it
is in 4 b-planes, it takes 2 entire updates to get the key. Is this because
I am using a library to read the keys? (I'm hoping that's not what it is,
because that would involve re-writing the keyboard routine to speed it up.)
Any Suggestions?
Faheyr@iubacsccplumb@spurge.uwaterloo.ca (Colin Plumb) (09/24/90)
The problem lies in the fact that you're using high resolution (640 pixels across) with 4 bitplanes. When this happens, the video data is using most or more of the chip memory's time, leaving very little for the processor. If you can get everything to run out of true fast memory (and not the fake fast memory you get in Commodore-supplied 1-meg machines), you won't have much of a problem, but the keyboard itself is still on the chip memory bus. If you can possibly switch to a lower resolution or fewer bitplanes, it would be the simplest solution. -- -Colin