Maximum screen size that works

[PhilRanger]

Hi everyone,

The VIC's default screen size is 22X23. Now it can be expanded by appropriate pokes, as nicely explained in vintage Compute! magazines and al.

But if you inflate it too much, you'll lose some things because they are going to be "outside" the tv screen.

What is the maximum size that is safe to use. I think it probably depends on NTSC vs PAL, monitor or regular TV, exact tv setups, etc. I want to find what I can safely assume to get just a bit more than 23X22.

Thanks!

[Boray]

http://user.tninet.se/~pug510w/datormuseum/overscan.zip

http://sleepingelephant.com/ipw-web/bul ... php?t=2787

http://www.soundclick.com/members/defau ... &id=321672

http://www.soundclick.com/members/defau ... &id=321675

http://www.soundclick.com/members/defau ... &id=321676

http://www.soundclick.com/members/defau ... &id=321677

http://www.soundclick.com/members/defau ... &id=321680

[Mike]

On the other extreme, one thread here in Denial featured an NTSC setup with a B/W CRT which could barely show more than the standard screen size.

For a PAL VIC-20, 26x32 characters is about the maximum you can display on most CRTs. With NTSC, much less, more like 24x28 characters.

If you reposition the screen, the necessary values for the registers $9000 and $9001 are different for PAL and NTSC. The kernal ROM contains the default VIC register values at $EDE4..$EDF3. For example, if you show 24 columns, you'd shift the x-position 1 character to the left to recenter the screen, as follows:

Code: Select all

POKE 36866,(PEEK(36866)AND128)+24 ; display 24 columns
POKE 36864,PEEK(60900)-2          ; 2x4 pixels to the left

... which works on both PAL and NTSC.

[PhilRanger]

So if I stick to 24X28 I should be safe and get a bit more playfield. Thanks!