I bought a Gecko 712/60 when it came out as the 'Developer Station',
a bundle with all HP Developer Tools etc back in 96.
I actually have 2 Geckos, used to have a K460 and a K58? as well,
I worked for HP Secure Internet Division for a few years...
I also still have a C110 and a C180.
I was surpised how good NextStep 3.3 is really working on 712/60,
even if I only have 80MB memory in it.
Sparc wise, I have a lot, so I installed OpenStep 4.2 on my SS20, put in one of my CPUs from SParcCenter 2000E a SM81-2 (85MHz SuperSparc II with 2MB Cache (only 1 can be used per bus)), and I assume that is the fastest processor you can put into a Sparc.. (I have 20 of these in the 2000E!).
It would have been fun if there was SMP support, or support for HyperSparc (ROSS/Bridgepoint), got Quad 180MHz HyperSparc for SS20!
The specs for them is quite good, taking the SS20 to new levels...
Or support for the sun4d Architecture, I have a Sparc Center 2000E System fully loaded, 20CPUs! (SM81-2) with 5GB of Memory! It runs Solaris 8 fine, but support from Linux is no longer there...
I also have a SS1000E with 8 CPUs...
And of course tons of other SS10s and SS20s, 2 E4500s with Fiber Disk Arrays...
But unfortunately not supported by NS/OS, I would love to see it booting the SS2000E :)
Wish everyone a Happy New Year!