Metal Slug boot problem/EPROM questions

mikey

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Jun 19, 2012
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I have a Metal Slug MVS boot where the sound cuts out part way through the second level. In the UNIBIOS jukebox all the music plays fine. I have replaced the M ROM, and the problem is still there. The only big difference I noticed is that the cartridge uses 4 27c160's for the V ROMs, where the MAME dump has two 4MB V ROM files. I know the files were split because you cannot use a 27c322 for V ROMs as it is 16 bit only. I just am not sure if this is some sort of addressing or bankswitching issue due to the roms being split up? Should there be some extra decoding that is not happening? I have tried to learn more about bankswitching, but am finding it hard to answer this question for myself.

As a side note, if splitting files to use over multiple eproms is possible, is it also possible to load multiple ROM files onto a single eprom to save chips? For example, if I had a game that used two 1MB V ROMs or four 1MB C ROMs, could I put the V1 and V2 on a 27c160, or the C1, C2, C3, and C4 files all onto a 27c322 and have it work? (obviously the PROG or CHA board would have to support EPROMs that size). Just curious...

Thanks! Sorry if this has been covered, I tried to search ahead but couldn't find this info.
 

Xian Xi

JammaNationX,
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Dec 1, 2005
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It could be the program rom itself. If you have the ability to verify the roms I would start with the P rom and also could be the data on the V roms were split wrong or put in the wrong order.

If the original board had 2 x 32mbit eproms then V1 becomes V1 and V2 and the original V2 when split becomes V3 and V4. Then the correct jumpers need to be set as well.
 

mikey

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Jun 19, 2012
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215
I just noticed that the program board is a PROGTOP, not a BK1 like the original calls for. Not sure if that makes any difference, but I can't find the jumper info for PROGTOP boards on the neo geo dev wiki to ensure the jumpers are set correctly. It looks like the capacitors by the M1 and S1 chips are missing (PC9 & PC10), along with some of the jumpers not being set correctly on the CHA256 board (according to scans at gotwalls.com). I don't think I'll have time tonight to take the chips out and verify them, but I'll try to get to it within the next few days. First I think I'll reset the jumpers and see if it makes a difference.

Thanks for the fast reply!
 

smkdan

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It can't be a V ROM problem since it plays fine in jukebox. V ROM issues would mean loud static playing instead of proper instruments/sound effects etc. You'd still hear some proper game audio even if V ROMs were pulled out completely, it won't be silent. If sound cuts out completely like here then it's a program issue especially if it happens at a precise point in the game. Try a unibios CRC check and see if it passes before doing anything with the P ROM.

You can load several smaller ROM images onto a larger chip like you said but you have to set the jumpers on the board to match the largest chip. See this CHA256 page for an example. You can't run C ROM on a single chip though. There must always be atleast 2 and it's always in pairs so you'd use 2x 27c160 instead of 1x 27c322.
 
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mikey

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Well, I reburned the P rom and all the V roms just to be safe (following what Xian Xi said about splitting and placing the V roms), and the problem is still there. I checked the jumpers on the CHA256 and they seem ok, but I can't find the info the rest of the jumpers (the only info on the wiki referred to J5-J10), and I can't find any info about the jumpers on PROGTOP boards.

The weird thing is, sometimes the game runs fine and the sound doesn't cut out, sometimes the music cuts out but not the sound effects, and sometimes I lose both. I cleaned the contacts again, and both boards with acetone just to ensure there are no shorts or something due to flux. I ran the CRC check like you suggested, smkdan, and everything came back ok.

Not sure what's going on... thanks for the replies so far though, they have been very helpful
 

Xian Xi

JammaNationX,
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Dec 1, 2005
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Well, I reburned the P rom and all the V roms just to be safe (following what Xian Xi said about splitting and placing the V roms), and the problem is still there. I checked the jumpers on the CHA256 and they seem ok, but I can't find the info the rest of the jumpers (the only info on the wiki referred to J5-J10), and I can't find any info about the jumpers on PROGTOP boards.

The weird thing is, sometimes the game runs fine and the sound doesn't cut out, sometimes the music cuts out but not the sound effects, and sometimes I lose both. I cleaned the contacts again, and both boards with acetone just to ensure there are no shorts or something due to flux. I ran the CRC check like you suggested, smkdan, and everything came back ok.

Not sure what's going on... thanks for the replies so far though, they have been very helpful

Burn yourself a diagnostics bios if you haven't already along with the additional M1 for testing the sound circuit. There could be just a problem with your mobo like a corroding trace, bad ram or failing Z80/YM2610.
 

mikey

Marked Wolf
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Jun 19, 2012
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You can load several smaller ROM images onto a larger chip like you said but you have to set the jumpers on the board to match the largest chip. See this CHA256 page for an example. You can't run C ROM on a single chip though. There must always be atleast 2 and it's always in pairs so you'd use 2x 27c160 instead of 1x 27c322.

Sorry to revive my own old thread, but I'm just wondering about this. On CHA 256 and 512 boards, do you combine C roms 1, 3, 5, and 7, and 2, 4, 6, and 8? Or do you combine them sequentially, 1-4, and then 5-8?
 

Xian Xi

JammaNationX,
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Dec 1, 2005
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Sorry to revive my own old thread, but I'm just wondering about this. On CHA 256 and 512 boards, do you combine C roms 1, 3, 5, and 7, and 2, 4, 6, and 8? Or do you combine them sequentially, 1-4, and then 5-8?

Odds and evens.
 
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