Played with the SGI Indigo2 I recently got.
Thanks to ths, who made me a matching serial cable and cracked the IRIX installation that already was on that machine. So I only had to figure out how to make this particular kind of Unix talk to the other machines in my network before I went on to try booting Linux/MIPS on it.
Sadly, It seems that the Indigo2 R10000 PROM doesn't like 32-bit Kernels.