Rairii, 3 months ago

i just found by a google search some old internal apple documentation about the OF ROM of the blue&white powermac G3

...it defines "MacOS-X" as: UNIX-based MacOS; think of it as "Mac OS NT".

it also mentions putting the macio MMIO physical address at 0x80800000 "to boot NT just in case" haha

it also mentions that OF's little endian mode "actually works in OF"

looking at the disassembly of the B&W's init code i have, it actually should work!

basically, when little-endian is set, after setting MSR[LE] it will set bit 5 (LE_MODE bit, turns on little endian) to PICR1, by using CONFIG_ADDR/CONFIG_DATA writes, and only uses every second instruction to do that (with each other instruction being a nop mainly) because of how MSR_LE works

in fact it seems the bootrom of every ppc mac after this has the exact same code, even those that use a different memory controller, no WONDER little-endian? is notorious for bricking lol