The Classic, LX and the single processor models of the SS20
are still supported under some version of SunOS 4.1.x.
A lot of people wanted these machines but only if they ran
SunOS 4.1.x. When the Classic/LX came out, clone manufacturers
were able to provide SunOS 4.1.x with it, Sun came out with
SunOS 4.1.3C some time later.
The Classic, LX, SS4, SS5 and SS20 are supported in the most recent
Solaris 1.x release, SunOS 4.1.4 (Solaris 1.1.2). The Classic and
LX are supported since 4.1.3C (release for LX & Classic only), the
SS20/SS5 since release 4.1.3_U1 rev B (Solaris 1.1.1B). The SS4
and SS20 with HyperSPARC since 4.1.4. Note that none of these OS
versions support SuperSPARC MP or any of the new graphics hardware
(ZX, TZX, SX, S24). The TCX adapter is only supported as a
cgthree, and SunOS 4.x doesn't use all its acceleration features.
The Voyager is not supported under SunOS 4.1.x, too many new device
drivers have been added plus the suspend resume feature.
The XDbus machines SS1000/SC2000 are also not supported under
SunOS 4.1.x. Support for their kernel architecture and XDBus is
missing in 4.x.
The UltraSPARC based machines are not supported under SunOS 4.1.x.
The new supervisor mode instructions, the new MMU, buses and devices
are not supported under 4.1.x.
Sun acquired the Business Systems Division of Cray Research and once
supported the Cray CS6400, a 64 SuperSPARC machine that runs a modified
version of Solaris 2.x, known as "Cray Solaris".
The largest Solaris 2.x machine you can currently buy from Sun is the
E25K, a machine that supports upto 72 US-IV
(x2 cores) cpus, 576 GB of memory at the same time.
Fujitsu sells an even larger machines, now also resold by Sun.