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Subject: Re: Answers to Paul Suades Questions
From: Andrew Jamieson (ajamiesn_at_mira.net)
Date: 2001-12-09


>> What does the mod file do? How is it used to patch the code?

>I don't think it patches the code at all, I'm pretty sure the mod file is
the
>complete code. If you look at my notes page, you'll see the mod file
contains
>a complete exception vector table and fully runnable code.
>
>If the mod file was in fact a patch file, it wouldn't look like that. There
>would be a number of patch segments, and they would be difficult to make
sense
>of.
>
>Another thing that speaks against the patch theory is that everybody gets
>different ROM versions when they buy their Archoses. Mine is v3.18 and I've
>seen in posts on the yahoo forum that people now get v5.05 in their ROMs.
Yet
>for all these versions, the same MOD file works just fine. That would be
>almost impossible with a patch solution.

Ah, yes, of course. I had forgotten about that.

>> So, the mod must be stored in the DRAM - does this mean that all the code
>> is copied to the DRAM at boot, and then the mod is overlaid to patch
>> required bits?
>
>How about this theory:
>
>- The unit boots from ROM, with just the stack in (on-chip?) RAM
>- After boot, the ROM code looks for a MOD file on the harddisk. If it
exists,
>it's loaded into DRAM and executed.

Makes sense to me. So; internal ROM or not? And if so, what does it do
(descramble the code file?)?



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