21 Jun
2018
21 Jun
'18
3:35 a.m.
On 2018-06-20 18:55, Paul Winalski wrote:
On 6/16/18, Johnny Billquist <bqt(a)update.uu.se>
wrote:
I didn't try for pure I/O buses. But yes, the Massbus certainly also
existed.
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.
Right.
CI (computer interconnect) was the communications
medium for
VAXclusters (including the HSC50 intelligent disk controller).
But CI I wouldn't even call a bus.
DEC later introduced another interconnect system
called BI, intended
to replace Unibus and Massbus.
I think that is where my comment started.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt(a)softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol