Hi all, I recently had time to think about a colour RAM expansion for the C64 and what prospects it could offer, but I'm not sure if I got the logic correct, and also have very little info about the way the VIC grabs the colour RAM data. I see from the circuit that the VIC has dedicated lines from the colour RAM so setting up a palette table would be easy (ie use the 4-bit data to index a RAM/EPROM table and feed this into the VIC), but the only functions I could see would be to convert colour to grey or inverse.... My thinking was to create a mode where an 8k colour RAM buffer was possible, hence a 4bit colour byte was available for each byte in the hires map (of course only in MC hires would the colour RAM be of use). Doing this would increase the colour independence (without CPU intensive routines), but whether this would work or not depends on how and when the VIC actually grabs the colour nibble? Does any body know? Option 1a) would be if colour info was grabbed in parallel to reading the Video RAM and then stored within the VIC for the next 8 reads of the Hires RAM. This would mean an expansion is not possible Option 1b) would be if colour info was read in parallel with the video RAM, but one for each hires RAM byte... which would mean a counter is required Option 2) would be if colour RAM is always just the lowest 10 address lines, and hence if the next three address lines were connected, 8K colour RAM would be available ono-for-one with the HIRES reading (still have to devise a way to actually set the values, but the VIC would read it no problems) Anyone have any ideas? - Nick ---------------------------------------------------------------- PLEASE TAKE NOTE: The contents of this email (including any attachments) may be privileged and confidential. Any unauthorised use of the contents is expressly prohibited. If you have received this email in error, please advise us immediately (you can contact us by telephone on +61 8 9441 2311 by reverse charge) and then permanently delete this email together with any attachments. We appreciate your cooperation. Whilst Orbital endeavours to take reasonable care to ensure that this email and any attachments are free from viruses or other defects, Orbital does not represent or warrant that such are free from computer viruses or other defects. (C) 2000: Orbital Engine Company (Australia) Pty Ltd and its affiliates - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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