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 Post subject: Modify a rom... how to?
PostPosted: Sun Jun 10, 2007 1:42 pm 
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What software you use to modify / fix an RR rom?

There is somewhere a tutorial or some docs that explain how to do some changes in a rom?

Thanks...


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PostPosted: Mon Jun 11, 2007 10:04 am 
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You do it the hard way. Disassemble the original, patch the code, and reassemble.


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PostPosted: Mon Jun 11, 2007 12:08 pm 
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MagerValp wrote:
You do it the hard way. Disassemble the original, patch the code, and reassemble.

Ok, i like this way ... =)

But... if a rom it's 64kb isn't directly loadable with a c64 so... i think to use an emulator with some expansions or a PC/Aimiga software... But i don't know what software i need...

I try with IDA 3.5 for DOS and 4.3 for win but i not successfully made it... i don't know why... ida let me select only 80x86 type of processors... no 6502.

I don't know how to work -outside- a C64 with a disassembler for 6502 or how to work in a C64/Emulator with all the 64kb of a RR Rom or how to split a rom -correctly- in -workable segments-...


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 Post subject:
PostPosted: Mon Jun 11, 2007 10:11 pm 
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Yes, what you need is a crossassembler. There are dozens to choose from, and it has been discussed to death, so just search a couple of C= forums.

I don't have IDA Pro installed, but last time I checked 6502 was available. There are plenty of free disassemblers too though.

A list of crossdev tools can be found here:

http://www.npsnet.com/danf/cbm/cross-development.html

(and for the record, I personally prefer ca65 and da65, that comes with http://www.cc65.org)


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 Post subject:
PostPosted: Sun Jun 17, 2007 7:15 am 
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I've been using the ACME assembler for my patching activities. No good reason, really, it was just the first thing I downloaded.

The basic method is:

*= base
!bin "program" ; include binary
*= patchaddress ; this moves * backwards
;...patch code...
!align $ffff, patchaddress+maxlength, $ea

The !align directive establishes a boundary so that it's impossible to accidentally overflow the patch area. It also pads with NOPs which may be useful.


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PostPosted: Wed Apr 22, 2009 9:30 am 
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So, as I don't know much about this kind of stuff could someone give a barebone explanation about how to disassembe the rom to pieces, modify it and put it back together (all this in PC)? There is one small tweak I'd like to see in RR rom, but it seems only way to make it happen is to learn things hard way and try to do it myself.

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PostPosted: Wed Apr 22, 2009 10:44 am 
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Location: Denmark
well, you could try to tell us what this desired fix is - if it's useful for other people than you, someone just might do it for you ;-)


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PostPosted: Wed Apr 22, 2009 11:43 am 
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Nothing major, I'd just like to check if the disk filecopier routine still exists (old manual says it's just temporarily disabled, not removed) and enable it again, I know it's probably just plain original AR6 version as improvements to the code have been on to-do list for years but it would still be useful to have at hand every now and then - it would be nice to be able to select drive(s) from all available devices instead of just 8 and 9 tho. I know it still can't handle >247 block files (ie. IFFL's w/ scanner) nor probably work properly with some 3rd party peripherals like CMD HD or IDE64, but it would still be better than nothing as I don't wanna fire up separate file copier program every time I want to cross-copy stuff between devices.

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PostPosted: Fri Apr 24, 2009 7:23 pm 
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the copier routines exist, but they do not work - thats why they are disabled in the first place =P

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PostPosted: Sat Apr 25, 2009 1:39 pm 
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groepaz wrote:
the copier routines exist, but they do not work - thats why they are disabled in the first place =P


So they are modified but not complete or bugfixed? Owww, that's it then.

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PostPosted: Sun Apr 26, 2009 3:54 pm 
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[quote="romppainen"][quote="groepaz"]the copier routines exist, but they do not work - thats why they are disabled in the first place =P[/quote]
So they are modified but not complete or bugfixed? Owww, that's it then.[/quote]

no, the problem is that they are NOT modified =) they broke when countzero modded the original AR rom to work with the additional ram of the retroreplay.

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