I'm bringing this up here cause I figure regular gamer folks who don't know how to program probably don't care what the difference is between the PRG and the CHR rom chips.
I have a copy of Castlevania, and R.C. Pro Am. I've cleaned both these carts several times, but each of them continue to have problems. Castlevania, once you get to the grim reaper level, will sometimes crash somewhere in that level.
R.C. Pro Am will always run fine and never crash, but the name tables and sprites sometimes get completely garbled up.
I took apart both carts this evening, and looked very carefully at the connectors. It appears that there was still a tiny bit of corrosion on a connector leading to the CHR rom on R.C. Pro Am, which would explain the garbled graphics.
And, on the Castlevania rom, there did appear to remain some corrosion on connectors leading to the PRG rom.
So I thoroughly cleaned those connectors that I apparently missed before. R.C. pro am doesn't seem to be getting garbled anymore. I have yet to verify if Castlevania will crash, because this has always been a very intermittent problem.
However---is it true that if JUST the CHr rom pins are dirty for example that the code will run fine, but the graphics will be messed up?
ZomCoder wrote:
is it true that if JUST the CHr rom pins are dirty for example that the code will run fine, but the graphics will be messed up?
Yes, if the game uses CHR-ROM data exclusively for tiles. Most later games respect that, but some older games (specially the ones on NROM and CNROM boards) stored miscellaneous data in CHR-ROM because they ran out of PRG-ROM space.
SMB, for example, is known for using some of its CHR-ROM to store its title screen layout. Depending on how that data is encoded, you could simply get a garbled screen or the game could even lock up in case invalid compressed data was read. If a game used CHR-ROM to store level maps or things like that, the gameplay could certainly be affected.
I've been looking at the CHR-ROM data of many CNROM games, and many of them contained information that was not tiles. These games would probably have problems in case there were contact problems in the CHR pins.
You have Castlevania PRG0, which I've heard has this crashing problem. Your cartridge is fine. PRG1 fixes this bug I believe.
If the CHR pins are dirty, many games won't give a shit. However it is possible some games may check the contents of CHR ROM, sometimes for anti-modding purposes, sometimes to be sure the right bank is switched in. If this happens the game may fail to run when CHR connection is poor.
So I suppose if I wanted to have a Castlevania cart that does not crash, I would need to keep buying used copies until I found one that has PRG1 written on the prg chip? (is it even written there?) Or perhaps make a repro using a PRG1 rom..haha
This happens on newer games too: witness "the wrong game card" error when importing a character into Animal Crossing: Let's Go to the City PRG 0 (Australia). Nintendo announced warranty replacement for game discs with this defect. I think that's why DS games have their PRG version written on the back of the Game Card. But unfortunately, I don't know when Nintendo started the practice of putting the PRG version on the label.
They started that practice on the NES days, by placing "A" or "B" stamps on revised cartridges. Altough more rarely sometimes there is revisions of the package that have the same PRG roms, as it's the case with Dragon Warrior III (U).
EDIT : Wow this is my 3000th post I should calm down and write less.
I played my castlevania cart last night and it crashed again in the grim reaper level. I took it apart, and sure enough it says CV 0 PRG on the prg chip. Does anyone have a copy of Castlevania that says CV 1 PRG?
I played Castlevania from my Powerpak also, it has not crashed yet. I wonder if there's any way I could determine if the ROM was ripped from a PRG1 copy? Maybe I could make a repro from that (or buy used copies in the hopes I snag a PRG1 copy)
ZomCoder wrote:
I played Castlevania from my Powerpak also, it has not crashed yet. I wonder if there's any way I could determine if the ROM was ripped from a PRG1 copy?
If the hash (CRC, MD5, SHA-x, etc.) matches the hash of the good dump of PRG 1, you have PRG 1.
I just wanted to report that I finally got R.C. Pro Am to never display garbled name tables. I must have cleaned the darn thing 15 or 20 times before its current, apparently working, state.
However I did one subtle thing different---I rubbed lengthwise along the connectors, rather than side to side, and I rubbed only in one direction, namely off of the cartridge.
My guess is that rubbing side to side as I did before was merely smearing whatever microscopic dust or corrosion remained on the connectors, rather than truly removing it.
Does this sound plausible?
I think I'll try this same technique on Castlevania 1, though I take heed to an earlier post that it may simply be a version that has a bug in the software itself.
ZomCoder wrote:
I think I'll try this same technique on Castlevania 1, though I take heed to an earlier post that it may simply be a version that has a bug in the software itself.
Don't bother; no amount of cleaning is going to fix your Castlevania cart. I've experienced the same crash on my PRG0 cart a couple of times. (Has anyone ever looked into why it happens?)
Finding a PRG1 cart is easy, though: PRG0 has five screws and the old circular Seal of Quality, while PRG1 has three screws/clips and the new oval Seal of Quality. I have both versions.
That's odd...I have 3 screws on my cart. Not sure what style the seal of quality is, will have to check that out. The PRG chip itself does say NES CV 0 PRG on it, however. Maybe there were more than 2 versions of the cart released. I'd like to get PRG1 also somehow. I think my rom of castlevania is prg1, because I play this on my powerpak and it has not crashed yet. I still want a working cart though