CHA42G Question

mikey · Mar 11, 2013

Is it possible to combine 6 4mbit C roms into 4 8mbit C roms that will work on a CHA42G board? I've been messing around with this board lately and was wondering about whether this was possible, and if so how you would combine the rom images to work? I know that this board addresses the C roms differently than other CHA boards.

Thanks!

Xian Xi · Mar 11, 2013

You have to mix the top and bottoms of the rom images.

mikey · Mar 11, 2013

I'm not sure I understand what you mean. How would you combine the roms in that way?

Xian Xi · Mar 11, 2013

What are you trying to do exactly?

mikey · Mar 11, 2013

I'm trying to combine the six 4 mbit eproms from a game onto four 8 mbit c roms to work on a cha 42G board. I'm not sure if it's even possible, because as far as I know c roms have to be done in pairs and combining these rom images would only require three 8 mbit eproms. I tried combining C1 and C2 for the first, C3 and C4 for the second, and then just doubling up the rom images for C5 and C6 for the final two C rom spaces, but that resulted in the graphics being all messed up.

Pedrobear · Mar 11, 2013

just do:
C1+C3 in C1
C2+C4 in C2
C5 in C3
C6 in C4

wyndcrosser · Mar 11, 2013

Mikey, I think he wants to know what game are you trying to "fix"

mikey · Mar 11, 2013

Haha, I'm "fixing" Magician Lord. Thanks for the replies, I'll try burning them in the order recommended by pedrobear

fremen · Mar 12, 2013

Hi,

I have a question mikey, is fine the sound??

Saludos

Xian Xi · Mar 12, 2013

Pedrobear said:
just do:
C1+C3 in C1
C2+C4 in C2
C5 in C3
C6 in C4

Don't forget that P14 and P15 are flipped on the 42G-1.

mikey · Mar 12, 2013

To swap P14 and P15, do you just change pins 54 and 55 on the neo 273, or do you swap pins 45 and 46 on the 273 like recommended on this thread? http://www.neo-geo.com/forums/showthread.php?239670-CHA-42G-1

Regarding the sound, last time I was able to mess around the sound wasn't working either. I've had issues getting the sound to work on the 42G while "fixing" certain games. I'm away for the week now though, so I won't be able to try any of this out until the weekend.

Pedrobear · Mar 12, 2013

Yeah you need to patch the Z80 code because of the ZMC chip.

mikey · Mar 12, 2013

I honestly would have no idea how to go about patching the Z80 code. Would that also explain how other games that originally use 42G-1 boards run with no sound on 42G boards?

fremen · Mar 12, 2013

Hi,

mikey said:
I honestly would have no idea how to go about patching the Z80 code. Would that also explain how other games that originally use 42G-1 boards run with no sound on 42G boards?

As far I know, 42G and 42G-1 are the same with regard the ZMC, the problem is to translate an M1 rom from a CHA32 to an M1 rom into a CHA42G, since CHA32 doesn't have a ZMC chip.

Saludos

Pedrobear · Mar 12, 2013

Both 42G and 42G-1 have a ZMC chip, so unless there's a factual difference between the boards revisions it shouldn't cause sound problems.

Xian Xi · Mar 12, 2013

mikey said:
To swap P14 and P15, do you just change pins 54 and 55 on the neo 273, or do you swap pins 45 and 46 on the 273 like recommended on this thread? http://www.neo-geo.com/forums/showthread.php?239670-CHA-42G-1

The bad thing is that P14 and P15 pins are also shared with A2 and A4 of the S rom.

This is what I had to do with a regular 4 x 16mbit roms(from furrtek):

If you want an eeprom only fix, I guess you can split the 4 C ROMs in half and merge them up like this:

C1new = C1 first half + C3 first half
C2new = C2 first half + C4 first half
C3new = C1 second half + C3 second half
C4new = C2 second half + C4 second half

Pedrobear · Mar 12, 2013

P14/15 are A19/20, why would that interfere with 8Mbits chips? A18 max here.

Xian Xi · Mar 12, 2013

Pedrobear said:
P14/15 are A19/20, why would that interfere with 8Mbits chips? A18 max here.

I'm posting general info for the boardset in case anyone uses the search engine.

mikey · Mar 12, 2013

Thanks for all the info, I'll give it another shot this weekend. I'm curious about patching the M1 to work with the ZMC chip though. Is that relatively easy to do? I'm pretty useless when it comes to programming, so it may be out of my league.

Pedrobear · Mar 12, 2013

Try out this file for M1

mikey · Mar 13, 2013

Awesome! Thanks a lot pedrobear. I'll try it and post if it works.

mikey · Mar 15, 2013

So I burned the C roms as suggested and now that part works perfectly. The sound still doesn't work, even with the new M1 rom, but that could be because I burned the V roms wrong... I *think* I burned V11 + V21 onto an eprom, and then did V22 on it's own... I have a feeling I'm way off on that one...

Pedrobear · Mar 16, 2013

You have to use one of the older boards without the PCM chip.

Xian Xi · Mar 16, 2013

mikey said:
So I burned the C roms as suggested and now that part works perfectly. The sound still doesn't work, even with the new M1 rom, but that could be because I burned the V roms wrong... I *think* I burned V11 + V21 onto an eprom, and then did V22 on it's own... I have a feeling I'm way off on that one...

What prog board are you using? EP?

mikey · Mar 16, 2013

The prog board is also a 42G... which has the pcm chip on it, so I guess the sound isn't going to work. It's the oldest board I had kicking around.

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