Ramlib Error #80000003 ?!?!

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Cymric wrote:
Mind, I remember trying to crack a game which featured a bootloader which had its code shifted by one byte to odd addresses. By installing a custom exception handler to pull in the other byte, then returning from that exception, the program could execute that instruction. Of course, execution speed is very low with the CPU excepting at every mnemonic. I was so impressed I gave up on cracking the program.

Hmmm, what reason was there to shift the code off by one byte? I don't understand how that would have "copy protected" it... :-?

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xeron wrote:

Hmmm, what reason was there to shift the code off by one byte? I don't understand how that would have "copy protected" it... :-?

Its so that crackers can't step over the code in action replay. An even cleverer trick is to put the code offsetted by one byte, then encrypt it. Your exception handler then not only compensates for the offset, but decrypts the code WHILE its being executed. In action replay, all you see in RAM is junk!

If the exception handler also re-encrypts the last executed instruction, there is NEVER a complete decrypted copy of the code in RAM.

Of course, on 68020+ it will just crash horribly.

Yeah I realised after I posted that It was probably to stop system monitors watching what's going on.

Another trick is to put the stack at an odd address and not use it so that the action replay can't be activated. (press the button on the action replay, NMI occurs, which causes a stack access, which causes a processor exception, so your machine gurus instead of going into action replay)

Hahahaha, yeah I figured that little trick out myself, somewhat accidentally ;-)

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Cymric wrote:
@browny:

Actually, I wasn't attempting to crack the program, now that I think about it. I was trying to insert some code so the power-led (and thus the low-pass filter) would be turned off.

Ahhh, the old "Trying to deactivate the filter" defence... It usually doesn't work when they see the "Trainer code" you've written ;-)

"Searching for Decrementing Opcodes? I don't know what you mean!"

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Cymric wrote:
@bloodline:

Heck, I wish I *was* good enough to write trainer code myself... That would have made quite a lot of games I bought with my hard-earned cash very worthwhile. Surely you remember a few games which were nice in concept, but utterly unplayable?

Hmmm, quite a few actually... "Castles" was one of my favourite games in that catagory along with "Life and death"... neither of those were "score" based so I couldn't figure out how to adjust them to my advantage :-(