Investigate RDRAM size logic

[bryanperris]

The N64 hardware writes the probed RDRAM size into GPR S6, then its stored in a special spot of RDRAM known as "os_boot_config_t". Right now the emulator (and like others) injects the RDRAM size just before the CPU hits the entry point.

What I think the IPL may be doing is triggering the system to probe and dump the result into a register. If this is true, then it would be possible to make the emulator listen for this trigger and write in the value into s6. I could check more into depth on this issue, if I ever receive my N64drive.