[stella] Please help with an overscan problem@bellsouth.net

[Dennis Debro <ddebro@xxxxxxxxxxxxx>]

I've been making good progress on Climber lately. Everything seemed okay on Z26 so I decided to try it out on my VCS via CC.

Everyting worked fine until the climber was within the 5 pixel zone of a ladder or when I played the death or success sound. The screen seems to lose sync or something. The top of the screen gets compressed to a few scan lines. It's almost like a vertical hold problem or picture tube problem.

These three routines are in overscan. When I moved the ladder checking to vertical blank the ladder problem went away but I still got the problem when the sound was played because that routine is still in overscan.

BTW, when I switch to using the PAL option (player 1 difficulty set to A) I don't see the problem. Also Z26 reports the correct number of scan lines each frame. I'm lost as to what the problem could be here.

My NTSC display is 262 scan lines (3 for vsync, 33 for vertical sync, 200 for kernel, and 23 for overscan. I tested this on a 4 switch VCS via CC with a Proline joystick (if that matters).

I'm attaching a zip file containing the binary and overscan source.

Any help would be *greatly* appreciated.

Take care,
Dennis

Attachment: climber5.zip
Description: Zip compressed data