gauging interest in VAX 6000-530

From: Carlos Murillo-Sanchez <cem14_at_cornell.edu>
Date: Mon Oct 25 12:07:33 1999

Chris Kennedy wrote:
>
> Mike Cheponis wrote:
>
> [snip]
>
> > See? There you go again! The 780's I/O was no great shakes. Sure, you
> > could stuff on a Fujitsu Eagle and do -pretty- good, but it was definitely
> > no speed demon. Since a dx2/66 is around 20 to 30x the integer performance
> > of that 11/780, I'm pretty sure the Intel part would crush an 11/780 in any
> > benchmark you could name.
>
> I note that we've ratched down from "any vax" to "11/780". TPC-C comes to mind...

Mike: you wanted numbers.

The 11/780 is one machine on which I do have a few recently acquired
docs. In page 2-2
of the 1977-78 VAX 11/780 architecture handbook there is a nice figure
of the cpu and
different interconnects. Basically, the cpu, main memory and I/O
subsystems were tied to
the Synchronous Backplane Interconnect (SBI), 13.3 MB/s, cycling at
200ns.
The console was attached to the CPU directly thorugh a separate channel.
Any device could request control of the SBI and control was granted
using a priority
scheme. The I/O subsystem could hold one unibus adaptor (1.5 MB/s) and
up to four
massbus adaptors (2MB/s each). The cpu had 8KB of two-way
set-associative write-through
cache (and the instruction set allowed for generation of very compact
code). The cache
monitored I/O <=> main memory transfers and updated accordingly.

Given this architecture, I think that there is reason to assume that an
11/780 might
service 100 users over serial lines faster than any 486-66 PC . Just
think of the interrupt
service overhead of 100 users typing simultaneously, even with 16 byte
FIFO buffers.

By the way, this little book is great reading... It really puts things
in perspective
to see the great 11/780 implementation 22 years ago...

Carlos.

-- 
Carlos Murillo-Sanchez    email:  cem14_at_cornell.edu  
428 Phillips Hall, Electrical Engineering Department
Cornell University, Ithaca, NY 14853
Received on Mon Oct 25 1999 - 12:07:33 BST

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