The 8051 is a very versatile µC, quite impressive for its time (second generation of intel's "single-chip Microcomputer", back at the beginning of the 80's), and to begin, it can run programs off its internal memory, off an external one, or from both, if you don't know how it is done on the design you want to modify or clone, you're lost. And it's just one of the three chips that can support many configuration schemes.
I don't know about asics, but this one probably deals with the way the Flash chip is accessed by the 8051, since it can't directly adress more than 64kB of data and 64kB of code on its external memory bus (except if expanded 16bit commands are used), it may also host a letterbox system and some other buffers and bus logic.
The Xeno GC is based on an AVR µC, I don't know that familly, but it seems it can't adress external memory other than SPI based, because of the 28pin package, and that limits its speed if not the memory size.
With such a low background on the subject, wanting to do what you suggest is way high, you have better use your Qoob as it is or wait for Hyperboot PNP, you'll loose less time and money re-thinking things that other people more advanced have already done.
I have begun such a project, beginning from nothing and wanting to turn a phoneline terminal into a computer (8051 based
) after a short study that lead me to the conclusion not only it was feasible, but it was indeed anticipated from the MB design step!
I had to dig out the 8051 and VDP documentations, reverse-engineer the motherboard of various models, but now I'm stuck at the Rom study, because the learning curve is so hard, and it is very time consuming!
Undead Sega wrote: ↑Wed Feb 05, 2020 11:22 pm
Papy.G wrote: ↑Sun Feb 02, 2020 10:02 am
That depends on what you mean by Qoob bios. The way the "chip" behaves is dictated by the code contained in the 89C51 rom (it is internal flash, as suggested by the 9, 80C51 would be a OTP one, for example) combined with the ASIC configuration and board topology. If you want to know where the payload (the code injected in the gamecube to "fool" it, it is probably somewhere in this 29xx chip.
What I meant by Qoob bios is the actual Qoob file(s). And if you say these are in the AM29LB160DB, then what is the purpose of the ASIC and 89C51 chips (and what code is in this)?
Application Specific Integrated Circuit is quite self-explanatory, the rest of the answer was already in my previous answer.