20 Jun
2018
20 Jun
'18
10:55 p.m.
On 6/16/18, Johnny Billquist <bqt(a)update.uu.se> wrote:
After Unibus (if we skip Q-bus) you had SBI, which was also used both
for controllers (well, mostly bus adaptors) and memory, for the
VAX-11/780. However, evaluation of where the bottleneck was on that
machine led to the memory being moved away from SBI for the VAX-86x0
machines. SBI never was used much for any direct controllers, but
instead you had Unibus adapters, so here the Unibus was used as a pure
I/O bus.
You forgot the Massbus--commonly used for disk I/O.
SBI on the 11/780 connected the CPU (CPUs, for the 11/782), memory
controller, Unibus controllers, Massbus controllers, and CI
controller.
CI (computer interconnect) was the communications medium for
VAXclusters (including the HSC50 intelligent disk controller).
DEC later introduced another interconnect system called BI, intended
to replace Unibus and Massbus.
As we used to say in our software group about all the various busses
and interconnects:
E Unibus Plurum
-Paul W.