CNROM (mapper 3) graphical glitches

Are you new to 6502, NES, or even programming in general? Post any of your questions here. Remember - the only dumb question is the question that remains unasked.

Moderator: Moderators

Post Reply
User avatar
lord_Chile
Posts: 120
Joined: Thu Feb 02, 2006 7:07 am
Location: Chile (South America), Quilpué
Contact:

CNROM (mapper 3) graphical glitches

Post by lord_Chile »

Hi!

Im developing a nes emulator. I can run NROM and UxROM succesfully. CNROM seems easy, and i can "play" CNROM games but all my CNROMS (circus charlie, friday13th and more) are experimenting graphical problems (glitches). I think my routine (8kb bankswitching is Ok)...

Only one detail. Im not using pointers for it, so im doing bankswitching by "copying 8kb chunks" to vram. Could be it?

So in your experience, Why CNROMS could experiment graphical glitches?
Good day to nesdev people. Lord..
Author of nothing =P
UTFSM Sansano programmer.. lord_Chile
Saludos a la Sede JMC de la UTFSM... Viña del Mar, CHILE
na_th_an
Posts: 558
Joined: Mon May 27, 2013 9:40 am

Re: CNROM (mapper 3) graphical glitches

Post by na_th_an »

I'm no expert, but being a developer which has used CNROM extensively, maybe it has to do with the fact that bankswitching can be done *at any time*, even during rendering, as it doesn't involve writing to the PPU at all. What kind of glitches are you getting? Maybe the 8Kb copies are taking longer than expected during a tight and timing sensitive routine such as generating the display?
User avatar
MottZilla
Posts: 2837
Joined: Wed Dec 06, 2006 8:18 pm

Re: CNROM (mapper 3) graphical glitches

Post by MottZilla »

Post a picture if possible. Your banking routine could be flawed or your rendering. Copying data is not a good idea. It's possible you are copying over and corrupting data maybe. Or post code from some of your routines.
Post Reply