Super Skidmarks NTSC patch

[ComradeOj]

I decided to take a shot at making the game run on NTSC systems. I think I got it working.

What I did:

In various parts of the game, the program sets the VDP to use V30 mode. This makes the screen roll on NTSC, so I patched it to use V28 mode. This may cause some screen cropping though.

That was only half of the trouble. There was also a DMA transfer routine that caused the screen to fill with garbage on NTSC. I'm not sure why. I just cut the entire routine out, and surprisingly the game still played. The offending routine can be found at $1F910C in the ROM. It only seems to be called from the HBLANK routine.

This is the offending instruction: MOVE.L #$7C000083, $4(A0)

At the time of execution, A0 will have the VDP data port ($C00000), which means that the instruction is writing to ($C00004) which is the VDP control port. I'm fairly certain that 7C000083 is telling the VDP to start a DMA transfer. I'm not sure of the source/destination though. All I know is that the game went to hell when it happened.

Another issue is slowdown. There was some pretty nasty slowdown going on. I'm guessing it's because the game has to draw 60 frames per second instead of 50. I flipped my overclock switch to 10MHZ, and it ran fine though. I'm also assuming that there is some NTSC speed-up going on, since the game and music was made for 50. I don't know for sure since I'm not too familiar with the game.

I also didn't patch out any artificial region locking. I'm not sure if the game even has a region lock. Please let me know if you run into any issues, so that I can fix them.

I might make a V2 patch some time in the future that addresses the DMA problem instead of just cutting the routine out, and also fix the slowdown issues.

Here is the download link to the IPS patch: https://drive.google.com/open?id=0B-...GUyNHhERUg0VEE
I used LunarIPS to make the patch, if it matters.

Video:

[saturndual32]

Finally had some free time to try the patch, but i must be doing something wrong, since the patched file gives me the exact same result as the unpatched rom on my mega everdrive . I will try again tomorrow.

But jugding from the video, you already did a great job. Thanks!

[saturndual32]

Tried to get the rom to work one last time before going to sleep, and it did!. Its nice to finally be able to play the game in color, instead of black and white, although other problems arise, as ComradeOj mentions. Anyways i am off to bed with a big smile on my face having played Super Skidmarks in color for a good 15 minutes.

Thanks ComradeOj!

[Benjamin]

I also didn't patch out any artificial region locking. I'm not sure if the game even has a region lock. Please let me know if you run into any issues, so that I can fix them.

The game isn't region locked. When I got mine in, I tried using a converter cartridge hoping that maybe it still needed to be in a PAL mode to play despite booting just fine.

Is there any possibility of a Game Genie code incorporating your fix?

[ComradeOj]

Tried to get the rom to work one last time before going to sleep, and it did!. Its nice to finally be able to play the game in color, instead of black and white, although other problems arise, as ComradeOj mentions. Anyways i am off to bed with a big smile on my face having played Super Skidmarks in color for a good 15 minutes.

Thanks ComradeOj!

Glad you got it working! I'll play around with it a bit more and see if I can get some of the issues smoothed out. I might be able to help the slowdown issue by having it not render the now off-screen portion of the game. Right now, you pretty much have to have an overclocked system to get smooth performance.

The game isn't region locked. When I got mine in, I tried using a converter cartridge hoping that maybe it still needed to be in a PAL mode to play despite booting just fine.

Is there any possibility of a Game Genie code incorporating your fix?

If I remember right, I had to make 7 words (14 bytes) worth of changes to the ROM. The Game Genie allows up to 5 words. I might be able to cut out two of the V30/V28 mode changes to hit that 5 code limit. That could cause issues in certain parts of the game. It's worth a shot though. Maybe screen rolling could be tolerated in the menus if the rest of the game was patchable to play correctly with only a game genie.

[Barone]

Sensational work, ComradeOj! Rep given.

The slowdown is "normal" since Codemasters usually pushed things quite a bit and this game was design around the 50 Hz mode and its longer VBlank time.

[Stef]

Super Skidmark is definitely a game using the advantages of the PAL system so i am surprised you were able to patch it for NTSC !
The DMA command you removed is probably the one used for splitted screen when you play in versus mode, i guess you broken it by removing the DMA command. You can just let the demo play to see the splitted screen versus mode...

[ComradeOj]

Super Skidmark is definitely a game using the advantages of the PAL system so i am surprised you were able to patch it for NTSC !
The DMA command you removed is probably the one used for splitted screen when you play in versus mode, i guess you broken it by removing the DMA command. You can just let the demo play to see the splitted screen versus mode...

You're right about the DMA being for split-screen. If you let the demo run, the splitscreen looks really glitched and freezes after a while. I guess I didn't notice because I was impatiently mashing buttons to skip to the game during testing.
I still want to try to fix the DMA issue, instead of just disabling it. I'm not sure why it glitches so badly when it runs. Maybe it's because PAL has a higher DMA transfer capacity than NTSC?

[Barone]

I'm not sure why it glitches so badly when it runs.

We're probably talking about tightly timed DMA transfers and VDP writes.
My blind shot is:
- In PAL mode it was writing stuff with display off.
- In NTSC mode VBlank time is shorter, so it's now writing stuff with display on which should be written only with display off, thus causing bad graphical glitches.

[Stef]

^^
This

It's why i said this game is specifically wrote for PAL system. I guess it relies on the extra VRAM bandwidth for the split screen mode.

[SEGA.GENESIS1989]

Glad you got it working! I'll play around with it a bit more and see if I can get some of the issues smoothed out. I might be able to help the slowdown issue by having it not render the now off-screen portion of the game. Right now, you pretty much have to have an overclocked system to get smooth performance.



If I remember right, I had to make 7 words (14 bytes) worth of changes to the ROM. The Game Genie allows up to 5 words. I might be able to cut out two of the V30/V28 mode changes to hit that 5 code limit. That could cause issues in certain parts of the game. It's worth a shot though. Maybe screen rolling could be tolerated in the menus if the rest of the game was patchable to play correctly with only a game genie.

ComradeOj, I was just wondering if you had any success developing an appropriate Game Genie code? Fingers crossed!

[ComradeOj]

ComradeOj, I was just wondering if you had any success developing an appropriate Game Genie code? Fingers crossed!

Yep! I don't call my youtube channel "Genesis Game Genie" for nothing.

I was able to omit two codes without issues that I could see. It still might screw the game up somewhere else.
These 5 codes should make the game playable. I don't have the physical game to try, but they worked on my everdrive using the game genie feature.

RVEA-JDE0
NVEA-JDHG
RWGT-JDAR
NWGT-JDDR
RRJV-86TN

These are the codes that were eliminated, in case anyone wants to experiment with which codes can be safely omitted.
RWJV-8DAA
RRJV-86TN

[SEGA.GENESIS1989]

Yep! I don't call my youtube channel "Genesis Game Genie" for nothing.

I was able to omit two codes without issues that I could see. It still might screw the game up somewhere else.
These 5 codes should make the game playable. I don't have the physical game to try, but they worked on my everdrive using the game genie feature.

RVEA-JDE0
NVEA-JDHG
RWGT-JDAR
NWGT-JDDR
RRJV-86TN

These are the codes that were eliminated, in case anyone wants to experiment with which codes can be safely omitted.
RWJV-8DAA
RRJV-86TN

Yee haaaaa! And here I thought that this PAL exclusive was unplayable! Thanks ComradeOj! I'll post my feedback in this thread when I get a chance!

You must spread some Reputation around before giving it to ComradeOj again.

Someone give this rep for me! He deserves it!

[ComradeOj]

Yee haaaaa! And here I thought that this PAL exclusive was unplayable! Thanks ComradeOj! I'll post my feedback in this thread when I get a chance!

You must spread some Reputation around before giving it to ComradeOj again.

Someone give this rep for me! He deserves it!

Thanks! I don't own the actual cartridge, I just test the game genie codes with my everdrive. I hope it works fine on the real deal.

A game not playable on my NTSC Genesis?


Some time I'll take a shot at some of the other PAL games with serious issues. I still want to play with skidmarks, trying to smooth out the issues it still has.

[SEGA.GENESIS1989]

Hey ComradOJ, I have some bad news: I just tried the GG code and the screen rolls right from the onset.