The high speed poke
would allow a Radio Shack Coco
or Color Computer
user to increase the execution speed of the microprocessor.
There were two 'Double speed' modes.
POKE 65495,0 would cause the processor to run at double speed ( 1.795 MHz ) when accessing instructions in ROM and Normal Speed ( 0.895 MHz ) when accessing DRAM.
POKE 65494,0 would deactivate the above mode.
POKE 65497,0 would activate a mode that allowed the Processor to run at double speed what accessing all memory. This was at the expense of DRAM refreshing and scrambled video. This mode was somewhat risky to use since the DRAM wasn't being refreshed by the SAM chip.
POKE 65496,0 would deactivate the above mode.
This also applies to the Coco 2 and Coco 3. The Coco 3 could run at true double speed mode without the Video or Refresh problems because of its enhanced graphics and memory management chip (GIME).