I was thinking about this, and, in this thinking, I came to conclude the lack of documentation is a major roadblock in mantaining obsolete systems. Sure, one can poke and probe and maybe eventually trace a fault. But sometimes, without docs, you're lost and hopeless. Shamefully, SiliconGraphics systems are scarcely documented.
Simple parts and boards can be fabbed, and new prototyping technologies are taking that further, however, we have not a chance of replicating the functionality of custom ASICs that weren't documented, even less so if the subsystem in which they're integrated is also a black box. Big multilayer PCBs are also still beyond reach of the poor hobbyist, so too bad for us.
R5000@180MHz, 256MB, XL-24, IndyCam
R10K@195MHz in broken teal case with broken purple bottom, XZ Graphics, missing: RAM, drives/sleds, case bits, PSU; awaiting completion [ATX PSU CONVERSION IN THE WORKS!]
misc: Some Sun
stuff, lots of x86 crap, one MSX
and a MSX2+
, a ZX Spectrum
clone, slotloader 400MHz
overclocked to 500MHz! iMac G3