Pretty decent document. It has all the registers,defines etc. But the only difficulty is that you need to be a very good assembler programmer to learn and at which I am not,but otherwise it is a very well documented text available on the R3000.
The infamous hitmen of the psx. These guys know a lot about the playstation and how it works down to the bone. They have some source code for the psx as well as a demo called 'Mother' check it out.
NAPALM! These guys are freaking psychadelic! They know everything along with a cool web page! GreetZ Go out to JackRippr,_Nik_,madman_,DANZ,#psxdev.