[Coco] [Color Computer] Re: POKE 65495,0

[Phill Harvey-Smith]

James Diffendaffer wrote:
> James, if your read back through the tread you'll find we were
> talking about running the CoCo 1/2 in SAM high speed mode with the
> RAM refresh disabled.
> 
> You can run a program faster this way but you have to enable the 
> refresh about every 4 to 4.5 seconds to keep DRAM from loosing it's 
> contents. The alternative is to do a read on each column at least
> every 4 seconds.  By my calculations, one read each interrupt should
> let 64K RAM hold it's contents just fine.  For 32K it could be every
> other interrupt.

I'm curious to know where the 4 seconds figure came from, the 4164 data
sheet I have a copy of says that the RAM needs to be refreshed every 4
miliseconds.....

> 60 interrupts / sec for NTSC 256 rows for 64K or 128 rows for 32K
> 
> That means it takes NTSC about 4.27 seconds to refresh 64K and half 
> that for 32K.  PAL might not be able to refresh a full 64K fast
> enough since it takes over 5 seconds using 1 read / interrupt.

However assuming that the above is true, it would be easy enough to do 2 
rows / int for PAL, though of course this would be slightly slower.

Cheers.

Phill.

-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.