How did they come up with PSP SDK?

[OopsIDied]

Hey everyone, I just recently got the PSP SDK installed, and I would like to ask how people came up with that. Was it leaked from Sony? was the assembly language used by the PSP an already well documented one? Did someone have to reverse engineer the assembly and make their own compiler? Thanks in advance. :)

[staticshade]

i believe it was all reverse engineered i don't know much else about it