Castlevania bug(?)

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Castlevania bug(?)
by on (#85515)
I spent a bunch of time over the weekend trying to fix what I thought was a bug with my emulator, but I'm pretty sure it's a bug in Castlevania.

Right before the last level starts, after Simon walks across the map screen, a bunch of garbage will briefly appear on the screen. I first noticed this after changing NMI timing to fix another game. I assumed I had a bigger problem since this glitch doesn't appear in Nestopia or Nintendulator.

It does, however, appear in a couple of youtube videos recorded off of real systems:

http://www.youtube.com/watch?v=5bzkUlwH ... re=related @ 0:08
http://www.youtube.com/watch?v=cezc5uq2 ... re=related @ 5:08

by on (#85516)
There's two different revisions of Castlevania, do they both behave the same way?

by on (#85517)
yes, tested both PRG0 and PRG1.

by on (#85518)
I don't recall it happening on my NES. Could it be as timing critical as to be affected by cpu/ppu relative sync? Maybe there is a recording of real hardware that won't have the glitch because of some sort of critical timing chance.

by on (#85519)
Just wanted to point out that it could be something to do with NTSC vs. PAL, I believe they have different refresh rates.

by on (#85520)
MottZilla wrote:
I don't recall it happening on my NES. Could it be as timing critical as to be affected by cpu/ppu relative sync? Maybe there is a recording of real hardware that won't have the glitch because of some sort of critical timing chance.

Maybe. Just found another one though:

http://www.youtube.com/watch?v=ONntlxVJS5g @ 21:19

by on (#85528)
I'm gonna have to try this on my NES.

by on (#85535)
I can only speculate it. SMB1 has a similar thing, just pay attention. Well, looks like the screen rendering seems to stay enabled for a few moments. Probably a programmer's error.

by on (#85536)
Castlevania is PRG only, it uses VRAM. No bankswitching, just CHR writes. Maybe they left the screen on for an extra frame before updating the nametables.

by on (#85541)
Dwedit wrote:
Castlevania is PRG only, it uses VRAM. No bankswitching, just CHR writes. Maybe they left the screen on for an extra frame before updating the nametables.


Right, my mistake here, I was with Castlevania 3 in mind. Sorry.

by on (#85543)
If it is an error, curious why it apparently only happens when that particular stage begins.