Help fixing an MVS cart

aha2940

aha2940

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Hi

I recently got an MVS KoF97 cart as broken. I thought the usual "clean it and it will be fine" but no. I opened it and found something...interesting:

- The CHAR board is from a KoF98 cart
- The PROG board is from a KoF97 cart
- The P1 chip is from Shock Troopers (!)

No clue what were they trying to do, but it's obvious why the cart didn't work. My question is: which EPROM can I use to replace the P1 chip? I already have a CHAR KoF97 board somewhere, so I can complete the cart and make it work again.

Thanks!!
 
kraquepype

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Cool thread, I was wondering where I could find Neo cart info... Thanks
 
aha2940

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Xian Xi said:
Can you post pics, I'd love to see that.
Click to expand...

Hi

Sorry for the delay, been busy with the job. Here's a pic of the PROG board (which is the interesting one). Notice I made a mistake: It was a KoF97 CHA board with a KoF98 PROG board. Also notice the Shock Troopers chip is socketed (!)



Regards.
 
GadgetUK

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LOL! I would start by removing that ST ROM. Will it even fit in the cart with a socket?
 
aha2940

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GadgetUK said:
LOL! I would start by removing that ST ROM. Will it even fit in the cart with a socket?
Click to expand...

Yep, it fits fine. There is enough clearance for sockets in the PRG board, but not on the CHAR board. I'll get the unencrypted KoF98 rom, burn an EPROM with the PN1 file and see if this works. If it does, bingo. If not...then something else is broken, LOL.
 
bustedstr8

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aha2940 your the new superstar of the tech threads.....where do you find all this $%&^$& bjorked stuff ? :p
 
aha2940

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bustedstr8 said:
aha2940 your the new superstar of the tech threads.....where do you find all this $%&^$& bjorked stuff ? :p
Click to expand...

Mostly from careless arcade operators from back in the day. For them these games just meant money, no matter if they were original or not or if they had serials/labels/nice shells or not. Also, when they broke it seems they tried to fix them at any cost, with funny results sometimes :)
 
aha2940

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Back on topic: I burned an EPROM (M27C160, I had no 27C800). Since the EPROM I used is double the rom size, I mirrored it twice, and put the EPROM in the PROG board socket. I got a known-working CHAR kof98 board and assembled the cart. It shows the unibios splash screen, then the NEOGEO logo (GigaPower) and then it just resets. It does not crash (no crash screen from the unibios), it just resets. There are no distortions either on the sounds or the graphics of the two screens it shows. What does that mean? obviously it means something is not working right, but what may I check?

Thanks!!
 
aha2940

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bustedstr8 said:
Did you use 242-PN1 61ac868a ?
Click to expand...

The very same:
Code: 
[gpulido@thrust roms]$ unzip -v neogeo/kof98h.zip 
Archive:  neogeo/kof98h.zip
TORRENTZIPPED-26ED6D9C
 Length   Method    Size  Cmpr    Date    Time   CRC-32   Name
--------  ------  ------- ---- ---------- ----- --------  ----
  262144  Defl:X    88914  66% 12-24-1996 23:32 4e7a6b1b  242-mg1.m1
 1048576  Defl:X   328988  69% 12-24-1996 23:32 61ac868a  242-pn1.p1
--------          -------  ---                            -------
 1310720           417902  68%                            2 files
[gpulido@thrust roms]$

However I did not replace the m1 chip with mg1.m1 from the same rom. Could that matter?
 
GadgetUK

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Check the jumpers vs MVS Cart Scans - also check the checksum in unibios to make sure its correct.
 
aha2940

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GadgetUK said:
Check the jumpers vs MVS Cart Scans - also check the checksum in unibios to make sure its correct.
Click to expand...

The jumpers are correct, but the CRC fails:



Can this be caused by the kof98 not being encrypted but the PN1 version? and why the first check is OK but the rest fail?

Edit: I just noticed the checksum thrown by the unibios is the same as the CRC32 for the ROM I burned in the EPROM. So I guess this means the rom I burned is OK but the problem is with the other P chip?

Edit 2: I just understood how the CRC are calculated. The P2 rom is taken, divided in pieces of 1MB (8Mb) each, and then the crc32 is calculated for each piece. I tested with my known-working kof98 cart, and the mame rom, got exact same results for all 4 pieces (banks). So, should I get the same results with this broken cart? I ask because my kof98 cart has the encrypted P1 chip, while the broken one does not have it encrypted, however the mame rom says the only differences are the P1 chip and the M1 chip.

Thanks!!

Thanks!!
 
Last edited:
GadgetUK

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That board doesn't provide any decryption, so the only thing I can think is the P2 doesn't match the P1. I think I would replace the P2 from the same ROM set you used for P1. Provided they are both unencrypted it should work. Not sure if those 74 logic chips are used for the P ROM access, or just V ROM access. The jumpers look correct. I guess there's also a chance that a trace under that socket is damaged?

Just tested mine - CRCs should be:-

61AC868A
1EFA8D4D
FFD65F8B
2E72246C
3B014944

Since yours are nowhere near the same I am guessing that maybe someone took the P2 from an encrypted cart, or maybe there are some missing traces leading to the P2 chip, or the P2 is faulty and was the original fault. Someone tried to swap out the P1 and it still didn't work, so they decided to try converting it to ST by swapping a single chip :P
 
Last edited:
aha2940

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GadgetUK said:
That board doesn't provide any decryption, so the only thing I can think is the P2 doesn't match the P1. I think I would replace the P2 from the same ROM set you used for P1. Provided they are both unencrypted it should work. Not sure if those 74 logic chips are used for the P ROM access, or just V ROM access. The jumpers look correct. I guess there's also a chance that a trace under that socket is damaged?

Just tested mine - CRCs should be:-

61AC868A
1EFA8D4D
FFD65F8B
2E72246C
3B014944

Since yours are nowhere near the same I am guessing that maybe someone took the P2 from an encrypted cart, or maybe there are some missing traces leading to the P2 chip, or the P2 is faulty and was the original fault. Someone tried to swap out the P1 and it still didn't work, so they decided to try converting it to ST by swapping a single chip :P
Click to expand...

Thank you GadgetUK. The CRCs you posted are exactly what I needed to be sure. There is no difference in the P2 chip of encrypted and unencrypted kof98 carts. Only the P1 is the difference. I replaced the P2 chip with one taken from a broken SF1 board (this board has encryption) and the cart now works beautifully :)

Thanks for the help guys, this community really rocks!!
 
Last edited:
GadgetUK

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Glad you sorted it! I've learnt something there - I had no idea the P2 wasn't encrypted on the board which implements encryption! =)
 
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