How does SPC2ROM work?

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psycopathicteen
Posts: 3140
Joined: Wed May 19, 2010 6:12 pm

How does SPC2ROM work?

Post by psycopathicteen »

From what I've been able to figure out using a tracing feature is that:

1) On bootup it loads the DP area with a custom routine.
2) That routine copies in DSP registers and then the rest of the 64kB of RAM.
3) Then it jumps to some routine placed in the middle of the 64kB of RAM that finishes the job by writing over DP registers, loading internal CPU registers and then jumping to the main code.

The 3rd step is what I don't understand. Does the SPC2ROM just looks for a bunch of bytes that aren't being used for the song, and then squeeze in it's own custom code? What happens when everything is completely filled up?
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jeffythedragonslayer
Posts: 344
Joined: Thu Dec 09, 2021 12:29 pm

Re: How does SPC2ROM work?

Post by jeffythedragonslayer »

How exactly did you figure out how step 3 works?
Myself086
Posts: 158
Joined: Sat Nov 10, 2018 2:49 pm

Re: How does SPC2ROM work?

Post by Myself086 »

That's a 6 months old question.

My question is: how did it not get answered already?

Nocash's Fullsnes explains it. I won't go into details until it's confirmed unanswered.
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