[Coco] POKE 65495,0

[Torsten Dittel]

> The article claims, "Also if you were using the upper 32k of ram, the
> double speed poke would wipe the memory." which is wrong. I ran some of
> my ml programs using the $FFD9 switch which ran both RAM and ROM at
> 2MHz. Video was lost during this period but immediately returned to
> normal when the clock rate was slowed. So RAM was not wiped.

Hmmm... AFAIR the memory refresh doesn't take place on a CoCo1/2 while
in the "RAM doublespeed" mode. I once wrote a BASIC programm rendering a
mirror ball hovering over a chess board. It took a whole day to render a
scene in PMODE4 resolution, so I decided to set the machine to
doublespeed (POKE65497,0 ???). The final picture had some "glitches" -
bytes in the video memory which had obviously "forgotten" their
information. However, a trick was to set the CoCo to this mode and slow
it down while in the IRQ handler (50(60) times a second). Apparently
this lasts enough time for memory refresh. There was a music tracker in
the RAINBOW using that technique (playing a great version of Axel F or
"The Entertainer" with 4 part harmony and different instruments).