Re: How to run the Dragon at double speed
Posted: Mon Dec 29, 2014 8:26 pm
I've just re read this in more detail (a bit more peace and quiet!). How long should I let the test program run for?zephyr wrote:Hammering at the break key during these tests is not a good idea because you are preventing the test code from restoring the computer back to normal speed (POKE65496,0:POKE65494,0). The point of these tests is to see if the computer runs stable enough at double speed to complete the test and return to BASIC with no corruption (or as little as possible) of the RAM contents. Random characters left on the green text screen screen after the test has ended indicate that the RAM has been corrupted during the test. A garbled screen during the test is normal. It is an indication that the computer has crashed if you can still see the garbled screen after the test has finished (The computer should always be powered off and back on again on again if this happens).Commodore wrote:With this one:
POKE65495,0:POKE65497,0:SOUND1,255":POKE65496,0:POKE65494,0
I got the tone but a garbled screen. It was non responsive to BREAK. After hammering the BREAK key for some time I got a garbled boot screen and silence was restored.
I pressed restore and the boot screen came back. I typed LIST, but the program was gone.
The most useful double speed mode is what is known as the "address dependent" mode (Switch to double speed with POKE65495,0. Return to normal speed with POKE65494,0). In this mode the computer runs the processor at double speed only when running code in ROM (The BASIC interpreter at $8000 to $BFFF or Cartridge ROM at $C000 to $FEFF). This mode is useful for running BASIC programs and Cartridge based software at nearly double normal speed.