The deskside "S/390" is the IS/390, which is
a PC running OS/2
containing a PCI card with an S/390 processor on it, and a bunch of
i960-based ARTIC960 CHANNEL-emulation cards. It doesn't really compare
with a full-size S/390.
I seem to remember something that was more than just a tower - it
might have weighed a few hundred pounds. Not a PC??
--
Will