On Aug 9, 2012, at 8:36 AM, Al Kossow wrote:
A 100U doesn't use a BW2 card, which was designed
by Sun Microsystems.
It uses the earlier SUN workstation card designed at Stanford. The 100U
was a 'brain transplant' for the original SUN-1 CPU card, replacing the
CPU with a Sun-2 CPU and memory, but leaving the rest of the cards alone.
Yes, and the "brain transplant" is an otherwise normal Sun-2 CPU, with different
boot ROMs to enable the bwone and parallel keyboard, rather than the bwtwo and serial
keyboard that would be used for an actual Sun-2. I.e., you couldn't do the upgrade
yourself today by taking a processor card out of a Sun-2 and plugging it into your Sun
100. You'd have to replace the ROMs, too.
A Sun-2 processor with Sun-2 ROM code and a bwtwo gets you a Sun-2. A Sun-2 processor with
100U ROM code and a bwone gets you a 100U.
Simply replacing one framebuffer with the other gets you no console video, though
presumably it would still work as a bitmap display for SunTools once UNIX loads, since the
driver code is present in the OS for both framebuffers.
The parallel keyboard interface is still present in the (multibus) Sun-2 but there are no
code paths in the ROM to activate it. The bwtwo apparently has a configuration register to
select a 1024x1024 framebuffer size, but I haven't found any information on how (or
whether) this is expressed in any of the jumpers on the card itself (or how to enable it
in software at the ROM monitor level) or whether this would even change the display timing
(I suspect it would have to). Presumably this is so folks upgrading a 150U chassis to Sun
2/170 equivalent could continue using their old monitors... but this is just a guess.
Technically I suppose you could do the same in the 100U but mechanically it's a lot
more challenging due to the way the I/O connectors are expressed on the back panel of that