[Coco] [Color Computer] POKE 65495,0

[Robert Gault]

James Diffendaffer wrote:

> I think the easiest way to make the highest speed poke work
> consistently would be to create an interrupt routine that would load
> from a different RAM address every few interrupts.  The address would
> change after each load so each column of RAM would be refreshed at
> least once in a 4 second interval.  At least that's about what my CoCo
> 1 could manage in that mode.
> 
> A better alternative would be to replace the SAM with a PLD and SDRAM
> making refreshes obsolete.  It would also open up a few possibilities
> such as even higher CPU clock rates by changing the divisor to 1, 2 or
> 4 instead of 8 or 16.  It would require a different CPU but we already
> know there are CPUs that handle 4MHz.  The PLD could also use the
> burst mode of the SDRAM to pre-load data for the VDG 4 bytes at a time
> to reduce it's use of the buss.
> 
> 
> 
> 
Success with the this high speed POKE may be model or unit dependent. 
All I can say is with my Coco1 F-board, I never had a crash with my 
programs when using this POKE although video was temporarily lost. There 
is even a specific recommended sequence for changing CPU clock rate 
given on page 11 of the MC6883 data sheet which I never needed to follow.