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Would it be possible to hack Contra japaneese (Gryzor) to use a MMC3 mapper instead of VRC4 and to be programmed on a TLROM card ?
Is there any accurate VRC4 doccuments ?

1. The Japanese release of Contra IS NOT GRYZOR - it is 魂斗羅, read as コントラ == KONTORA == Contra. Anyone who tells you that the Japanese version is named "Gryzor" is an idiot and/or a liar. (for the record, Cowering falls into the first category)

2. The Japanese version of Contra uses all eight 1KB CHR ROM banks to their fullest extent, so adapting it to MMC3 (which only has four 1KB banks and two 2KB banks) would require significant additional modifications.

What about RAMBO-1 or MMC5 or FME-7? Would it be straightforward to hack VRC4 games to run on those?

Quietust wrote:1. The Japanese release of Contra IS NOT GRYZOR - it is 魂斗羅, read as コントラ == KONTORA == Contra. Anyone who tells you that the Japanese version is named "Gryzor" is an idiot and/or a liar. (for the record, Cowering falls into the first category)

Thanks for correcting/clarifyng. Gryzor is the name of the unoficial engish translation from the japaneese one, right ? I also seen that Gryzor was the name of the arcade counterpart of Contra. So I think they renamed it for that reason ? At least the responsable to name roms under goodnes standards did wrong here.

Scince the game looks to have a bunch of empty /repeating space in CHR block, I'll take a look about this possibility a bit more, even if some character dupling will be needed, thanks for figuring that out.

The mapper most defintely has undoccumented IRQs setup trough $6000.
Could they be converted to MMC3 IRQs ?
Oh, yeah, the game is VRC2, not VRC4.

However, the game uses lower pattern table for sprites, so the MMC3's IRQ won't work until both pattern tables are swapped. Because the game uses 8x16 sprites, that implies changing their tile numbers.... adittionally I think that it would be possible to split sprite banks in 2kb banks instead of 1kb, but I'm not sure.... I'm pretty much discouraged, now.

Bregalad wrote:The mapper most defintely has undoccumented IRQs setup trough $6000.
Could they be converted to MMC3 IRQs ?
Oh, yeah, the game is VRC2, not VRC4.

Er, what are you talking about? 魂斗羅 does not use any IRQs at all, and it certainly doesn't have anything at $6000 - last I checked, my VRC2 mapper code did not emulate IRQs, yet the game runs just fine.

If you'd like I can send you a hacked (with "trainer") copy of the game. Probably wouldn't be much use as it requires 32K of CHR RAM to swap patterns in and out of, also it must turn off/on the screen to update the CHR RAM outside Vblank which creates distracting white flashes.

At least the game has some crazy writes and reads to $6000, and that register isn't doccumented.
This may let the game totally unaffected, who knows ?

I don't mean to state the obvious... but couldn't it be RAM? =P

I just tried Contra J after taking out RAM there and it never got to the title screen.

I'm sure it's not, because ONLY $6000 is acceded, and by the way, only the bit 0 of that register. There seems to be a little routine writing something to this register, then read it several times and do something with it between screens.
I now have a MMC3 rom, I hacked both PRG, and CHR/mirroring banking code, but only the PRG one seems to work fine, and the game has corrupted graphics.

I succeded, but now I'm unable to make the rom copatible with a PAL NES, after beating a stage where you got detailed portrait of the heroes, the games uses strange sprite zero hits and it don't work on PAL. Buh, I'm tried of this.

It's now 100% complete and usable for anyone who wants !!

http://jonathan.microclub.ch/contra

But unfortunatly, I couldn't test it on the real hardware yet because my EPROM programmer isn't getting working for a random reason.

It would've been nice if the game hadn't been erroneously renamed to "Gryzor" in the process...

That's fault of translators, not mine.
Actually, Gryzor is the name of the european arcade version, if I get things correctly.

I'm interested but the URL is timing out.