Maximum number of columns in 36866

[nippur72]

I found a reference in the VICE emulator source code suggesting that maximum number of columns for POKE 36866 is 33 on PAL and 32 on NTSC.

Can someone confirm this? (I don't have a NTSC machine to test it myself).

All is needed is a prog like this:

Code: Select all

10 POKE 36866, 33+127  : REM 32+127 for NTSC
20 POKE 36866, 34+127  : REM 33+127 for NTSC
30 GOTO 10

if the screen doesn't flicker it means that VICE is right, there are maximum values. (Decrease values by 1 to see it flicker).

[tokra]

You start getting corruptions on the real machine. It also depends of the volume in $9000. See here:

http://sleepingelephant.com/ipw-web/bul ... 99#p102486

For $9000 at 0 you start getting corruptions with value 34 on PAL and value 31 on NTSC. So the max for PAL is 33 and for NTSC is 30 - I confirmed both on actual hardware just now. Higher values are theoretically possible, but will lead to more or less corruption of the displayed image. The maximum visible image is 28 chars for PAL (224 pixels) and 25 chars for NTSC (200 pixels). See Maxiedit: http://sleepingelephant.com/ipw-web/bul ... f=2&t=8375