You really can't do that, so far as I know.

The SS20 takes Mbus modules, and the only CPUs on those are SuperSPARCs and
HyperSPARCs. The SS4 and SS5, by contrast, used MicroSPARC CPUs, possibly
socketed, but not on an Mbus module. The Supers and Hypers are multiple
instruction issue CPUs, and are a lot faster at the same clock rate than
the Micros; they also typically have lots larger L1 and L2 caches.

If you want to upgrade the SS20, go buy a faster Mbus module. Also, NetBSD
doesn't quite support the HyperSPARC CPUs yet, though it's being worked on.

	Erik <fair@clock.org>