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Last updated on Oct-18-2019 Download

Nes to Vs

Nes to Vs
by on (#135481)
Hello all,

I keep reading rumors about the possibilty to modify nes roms to play on VS hardware (unisystem / dualsystem). But have come up empty handed.

Has this been succesfully amploshed yet?
Re: Nes to Vs
by on (#135482)
If the game already reads from $4017 at least once every second it should mostly work on a 2C03 PPU anyway...

Adding things like "works with coins or DIP switches" or "supports other PPUs" gets grody rapidly, and there's a lot of minor differences between the Vs System and ordinary NES games that could trip up a random game.
Re: Nes to Vs
by on (#135513)
Why would you want to anyway?
Re: Nes to Vs
by on (#135514)
Perhaps if you have developed an arcade-style NES game, and your home town still has a local arcade, and you want to get your game in front of people or a successfully location tested arcade game on your resume.
Re: Nes to Vs
by on (#135515)
I thought it was clear that OP wants to convert something, not develop a new game. If you're starting from scratch, meeting the VS requirements isn't really a big deal.
Re: Nes to Vs
by on (#135522)
I have had a red tent on location for about 2 years. Have pretty much all the decent VS games installed at some point, and am constantly being asked now if "such and such" NES game can be installed.

Would be nice to have something like super dodgeball in there :)
Re: Nes to Vs
by on (#135523)
Super Dodge Ball is MMC1, as is Vs. Dr. Mario. Unfortunately, the MDS-VS1 board only supports 64 KiB PRG/CHR, and Super Dodge Ball is 128/128, so there would be some rework there...

Super Dodge Ball also stops reading from $4017 if you select a one-player game.
Re: Nes to Vs
by on (#135533)
Thanks for the notes, now I have a starting point at least :)
Re: Nes to Vs
by on (#135534)
A few pages on the wiki that might be of help:
A few pages about Vs System modules/games (you probably already know these):
NesCartDB for searching through NES/FC games:
Re: Nes to Vs
by on (#141472)
I did some work in this space recently.

I wrote a tool which will extract Vs. system size ROM files from iNES format files. Along with it I ran through all the iNES ROMs in my collection which matched a spec which I thought might work on Vs hardware.

The results are posted here:

Note that you'll need an RC2C05 variety PPU for the games to look normal. I was considering attempting to modify one of the games to work on alternative PPUs before I got distracted from this project.
Re: Nes to Vs
by on (#141479)
I don't think MAME implements the Vs system's watchdog? That could be a problem.

Also, do you mean 2C03?
Re: Nes to Vs
by on (#141490)
Quick reference:
  • 2C02 is the NTSC PPU.
  • 2C03 is an RGB PPU with NTSC timing and an approximation of the NTSC palette in correct order, used in Vs. Duck Hunt, Vs. Tennis, and PlayChoice. The most popular mod to produce RGB video from an NES used this PPU.
  • 2C04 is any of four RGB PPUs with differently permuted palettes, used in the majority of Vs. games.
  • 2C05 is a 2C03 with the B bus addresses of PPUCTRL and PPUMASK swapped, used in later Vs. games. It became popular among NES modders after it was discovered that the addition of an 8:1 mux (e.g. 74HC151) would make a 2C05 behave as a 2C03 or vice versa.
  • 2C07 is the PAL NES PPU, with the longer vblank, forced OAM refresh, swapped emphasis bits, and bug-fixed OAM DRAM controller.
Re: Nes to Vs
by on (#141638)
lidnariq wrote:
I don't think MAME implements the Vs system's watchdog? That could be a problem.

This is true. I've seen at least 1 game work in MAME but not on actual hardware - F1 Race. Although what I'm reading in the wiki indicates it might have worked if it was installed on the "master" side of the board. I should follow up with the person who did this test.
Re: Nes to Vs
by on (#141647)
The watchdog failing should look just like a CIC failure... i.e. runs for a second, resets, repeat forever.
Re: Nes to Vs
by on (#148317)
I once did it the other way around. I converted Vs. Super Mario Bros to an NES ROM a while back. There wasn't much too it. Someone else had already written the color pallet correction code, I just had to apply it to the correct place in the ROM with a hex editor and do various steps to compile it into a .nes file and hack it a bit to make it bypass the insert coin screen. The extra RAM on the Vs. system was not even a factor. I guess Super Mario Brothers doesn't use it. Duck Hunt on the other hand was over my head. I think someone figured it out, but it makes a high pitched noise if you try to run it on an NES. Something about it tries to detect the pistols and sounds an alarm if they're missing as an anti-theft measure.
Re: Nes to Vs
by on (#148320)
Super-Hampster wrote:
The extra RAM on the Vs. system was not even a factor. I guess Super Mario Brothers doesn't use it.
False! All emulators assume the cart wants RAM in the $6000-$7FFF range unless it's given a NES2.0 header with the explicit choice of "no extra RAM".