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MUG U.K(tm)
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Format of Meka Save game files.
Post Posted: Wed Mar 01, 2000 11:46 pm

Want to try and use the save game files so I can see what memory addresses are used so I can make the relevant trainer patches. What's the breakdown of the file ?

First 4 bytes = MEKA

But what else is stored after that ?

Many thanks.
 
  • Joined: 28 Sep 1999
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Post Posted: Thu Mar 02, 2000 4:41 am

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> First 4 bytes = MEKA

Disregarding the header and the trailing EOF, the
last 32K is the on-cart battery backed RAM, before that
is 16k of video RAM, and I'm fairly certain before that
is the 8K of system RAM.

Maybe future versions of Meka will have a built-in cheat finder
to help doing this. Or at least a function to dump RAM to disk,
like genecyst or NESticle. It's a shame that not many emu's
support cheat making. ;)


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MUG U.K(tm)
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Post Posted: Thu Mar 02, 2000 9:23 pm

Quote
>
> > First 4 bytes = MEKA

> Disregarding the header and the trailing EOF, the
> last 32K is the on-cart battery backed RAM, before that
> is 16k of video RAM, and I'm fairly certain before that
> is the 8K of system RAM.

What I do at the moment is examine a dead listing courtesy of Dz80 .. and then look for the usual ld a,#03 etc. and the subsequent dec's and sub's .. and nop them out .. or change the initial start value and then alter the ROM via an IPS patch. Would love to do it via the MEKA.PAT file, but really can't be bothered as it would mean constant updates to MEKA (similar to the UltraHLE .INI files)...

Is there a file compare tool (pref. DOS/WIN32 DOS) that will compare two files of same length, but only look for bytes that match the initial request ? I.e. compare two files, but only show changes where the original file had 3? Would make hunting down lives counters etc. a lot easier.

Also .. if the save game data is 24814 bytes .. how can there be 32K+ stored in it ?

What's the exact breakdown ?
 
MUG U.K(tm)
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Post Posted: Thu Mar 02, 2000 11:39 pm
Exact breakdown from the horses mouth (cheers!)

Quote
> Is there a TXT file explaining what memory (assuming C000 onwards) is stored
> in a Meka save game file ? Want to make some more trainers up (others I have
> done are attached) but finiding it difficult with only a Z80 disassembly
> listing to work from.

MEKA (4 bytes)
0x1A (1 byte)
version number (1 byte)
driver (0: sms, 1: gg, 2: sg1000, 3: sc3000, 4: coleco, 5: msx, 6: nes) (1
byte)
custom structures with lot of stuff (96 bytes)
RAM
VRAM
...

so it should start at 4+1+1+1+96

Now all I need is a decent file comparer so I can make some more trainers :)
 
  • Joined: 28 Sep 1999
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Post Posted: Fri Mar 03, 2000 2:34 am

Quote
> Is there a file compare tool (pref. DOS/WIN32 DOS) that will compare two files of same length, but only look for bytes that match the initial request ? I.e. compare two files, but only show changes where the original file had 3? Would make hunting down lives counters etc. a lot easier.

Under DOS you can do 'fc /b file1 file2 > diff.txt' for a list of different bytes between two files.
It won't work if the file size has changed (not that this will happen with Meka)

Quote
> Also .. if the save game data is 24814 bytes .. how can there be 32K+ stored in it ?

Games that don't use the on-cart RAM won't have the 32K saved, hence a smaller file.



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