11/782 (was: Any own an 11/725...?)

[a.carlini at ntlworld.com]

Huw Davies wrote:
> Certainly the only 11/782 I know of (Melbourne University) was split
> to get much better performance. Basically all I/O (and hence all of
> VMS) had to occur in the "master" 11/780 so all that could be run in
> the slave was CPU intensive jobs. As soon as your CPU bound process
> wanted to do something other than compute it had to be scheduled in
> the "master".

The 782 certainly was two 780s joined at the hip. I thought that the
SBI was joined up too but that might be the Purdue (?) VAX-11/784.

When proper SMP was introduced in VAX/VMS V5.0 (the previous support
for the VAX-11/782 being dubbed ASMP), the 782 support was dropped
and the choices were either don't upgrade or split into two 780s.

> Effectively you had one big global lock on VMS. The story goes that
> all the necessary VMS changes to support the 11/782 occurred over a
> weekend. Another interesting story concerns the mythical 11/787 (ie
> two 11/785s rather than 11/780s). There were rumors of such systems
> occurring in a mythical site somewhere near the centre of Australia

There would have been no reason that a "787" would not have worked,
but given that bad rep that the 782 had, why would anyone have bothered?

Interestingly I don't think I've ever come across any technical docs
that describe the 782. It does rate a passing mention in the VIDSM.
The various "how we wrote support for the 782" articles that I've read
fail to mention that it was done over a weekend :-)

Somewhere or other I have Kathleen Morse's "how we might do
[A]SMP in VMS" memo. I think the memo itself was long enough
to take a weekend to write!

Antonio


-- 

Antonio carlini
arcarlini at iee.org