A little bit of clarification - POKE 65495,0 speeds access to the ROM to 1.78 Mhz (like the Extended BASIC ROM), but RAM (your typed in BASIC program, for example) is left at the original speed. This is why the results aren't twice as fast. POKE 65497,0 speeds both up, but the VDG/SAM combo can't keep up for the video refresh, and if you have it on too long continuously you can have issues with the dynamic RAM refresh (a few commercial programs enable it for periods of time to speed up calculations and clock it back so that the RAM never gets lost. On a Coco 3, you can run the machine at flatout double speed with no issues (in fact NItrOS9/OS-9 Level II always runs in full double speed). There is an modern option called the "SAM DOUBLER" that allows even a Coco 1/2 to run at full double speed without the issues there is normally, which requires upgrading dynamic RAM to static RAM.
We used those pokes all the time on our Dragons to make basic programs run faster. I’ve never heard about them overheating or anything, but on some Dragons they wouldn’t work at all, the computer just froze.
A little bit of clarification - POKE 65495,0 speeds access to the ROM to 1.78 Mhz (like the Extended BASIC ROM), but RAM (your typed in BASIC program, for example) is left at the original speed. This is why the results aren't twice as fast. POKE 65497,0 speeds both up, but the VDG/SAM combo can't keep up for the video refresh, and if you have it on too long continuously you can have issues with the dynamic RAM refresh (a few commercial programs enable it for periods of time to speed up calculations and clock it back so that the RAM never gets lost. On a Coco 3, you can run the machine at flatout double speed with no issues (in fact NItrOS9/OS-9 Level II always runs in full double speed). There is an modern option called the "SAM DOUBLER" that allows even a Coco 1/2 to run at full double speed without the issues there is normally, which requires upgrading dynamic RAM to static RAM.
We used those pokes all the time on our Dragons to make basic programs run faster. I’ve never heard about them overheating or anything, but on some Dragons they wouldn’t work at all, the computer just froze.