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Old 08-02-2007, 04:18 AM   #1
The 9th Sage
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Default Converting a NeoGeo ROM into a NeoGeo CD game?

I'm going to take a guess and say this isn't possible (or isn't without a lot of hard work), but someone could feel free to prove me wrong. <img src=smilies/magbiggrin.gif> I've become curious about this.
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Old 08-04-2007, 01:47 PM   #2
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Default Re: Converting a NeoGeo ROM into a NeoGeo CD game?

> I'm going to take a guess and say this isn't possible (or
> isn't without a lot of hard work), but someone could feel
> free to prove me wrong. I've become curious about this.

i can see you wanting to do the reverse. but why rom --> CD unless it was to use on a real neogeo CD system. is it?

if so, wow man. you got some rare gear. <img src=smilies/magbiggrin.gif>
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Old 08-04-2007, 07:37 PM   #3
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Default Re: Converting a NeoGeo ROM into a NeoGeo CD game?

> i can see you wanting to do the reverse. but why rom --> CD
> unless it was to use on a real neogeo CD system. is it?
>
> if so, wow man. you got some rare gear.

Naw...there's a Gamecube NeoCD emulator, that seems to support JUST the NeoCD. :P I would love to be able to say I had the actual system, just for the 'street cred' if nothing else. <img src=smilies/laff.gif>
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Old 07-16-2008, 03:58 PM   #4
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Quote:
Originally Posted by The 9th Sage View Post
I'm going to take a guess and say this isn't possible (or isn't without a lot of hard work), but someone could feel free to prove me wrong. <img src=smilies/magbiggrin.gif> I've become curious about this.
It is possible for a small number of Neo Geo roms. The problem is that the roms has to fit into the memory of the Neo Geo CD. The limits can be found in this document:
[url]http://arcadedev.emuvibes.com/documents/neogeocd.html[/url]

I converted (and released) 4 games. The conversion were released by a HK company:
[url]http://assemblergames.com./forums/showthread.php?t=9428[/url]

Someone later wrote up a document describing the process:

MVS to CD Conversion How-To:
----------------------------

Here's a quick "How-To" to port Neo Geo MVS roms to a real Neo Geo CD system.

Iq_132 has made a quick step-by-step with tools to port MVS roms,
here's his details (taken from a page at the NeoSource Forum):

----------------------------------------------------------------------------

First, you must make sure that you are dealing with a very tiny neo-geo rom or
you will end up having to cut a lot of precious data out and will end up with
a glitchy game.

The "P" (M68K program) rom must be less than or equal to 2 Megabytes
The "S" (text) rom must be less than or equal to 128 Kilobytes
The "C" (sprites) rom(s) must be less than or equal to 4 Megabytes total
The "M" (Z80 program) rom must be less than or equal to 64 Kilobytes
The "V" (samples) rom(s) must be less than or equal to 1 Megabyte total

If the roms above are larger than this, you will have to remove and discard part
of the rom.

Now, onto the actual conversion:

M68K Program (P):

1. Byteswap the entire rom (swap byte 1 with byte 2, byte 3 with byte 4, etc..)
2. Swap two sets of bytes at address 0x66 and 0x6A of the program
3. Name your output prg.prg (Can be different)

Sprites (C):

1. Read two bytes from your C1
2. Byteswap the bytes from part 1
3. Read two bytes from your C2
4. Byteswap the bytes from part 3
5. Repeat steps 1-4 until your new rom is 4 Megabytes in size
A. Your output file may be smaller if your roms are tiny
6. Save the ouput file as spr.spr (Can be different)

Text (S):

1. Make sure your S1 rom is within the size-limit boundaries
2. Rename your S1 rom to fix.fix (Can be different)

Z80 Program (M):

1. Make sure your M rom is within the size-limit boundaries
2. Rename your M rom to z81.z80 (Can be different)

Samples (V):

1. You may only use one V rom, so if you have more than one, find a tool to
merge them
2. Make sure your (merged?) V rom is within the size-limit boundaries
3. Rename your V rom to pcm1.pcm (Can be different)


Lastly, you will need a few text files:

- IPL.TXT (This file is very important!)
- ABS.TXT
- BIB.TXT
- CPY.TXT

IPL.TXT is the most important, it tells the Neo-Geo machine which files to
load first, it usually contains something similar to this:

FIX.FIX,0,0
Z81.Z80,0,0
PCM1.PCM,0,0
SPR.SPR,0,0
PRG.PRG,0,0


----------------------------------------------------------------------------

After doing all that, you need to take the xxx.PRG file and open it up with
a HEX editor and change 14 bytes. I've checked the "conversion" of JoyJoyKid
of CDoty and found that he changed 14 bytes between 0x0042 to 0x0063, which is
part of the boot sequence (IRQ). I've compared it to the "L.PRG" file found in
"ADK World CD" and the changed bytes matches exacty except the 0x0063 which
CDoty replaced with the byte [E0] instead of byte [32]. The [E0] can be found
in any AES N0xxxx1A.038 ROM.

Here's the list of the bytes to change needed to boot on a real Neo Geo CD:

Adress: Original Byte: New Byte:
-------------------------------------------------------------
0x0042 04 05
0x0043 26 22
0x0046 04 05
0x0047 26 28
0x004A 04 05
0x004B 26 2E
0x004E 04 05
0x004F 26 34
0x0052 04 05
0x0053 26 3A
0x0057 26 F2
0x005B 26 EC
0x005F 26 E6
0x0063 (*) 32 E0
-------------------------------------------------------------

(*) = The 0x0063 can be changed to either [E0] which tells
the CPU that's the game is a AES version or with [32]
which tell the CPU that's is a MVS/CD version.

Now, with these changes, you will be able to boot any MVS-to-CD port.

Last edited by cdoty; 07-16-2008 at 04:07 PM.
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Old 07-17-2008, 03:01 AM   #5
The 9th Sage
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Aaah, interesting. So it IS possible, just not with the games I'd want to convert. Thanks for bringing the post back, I never was able to find any concrete info on it.
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