24 Oct
2005
24 Oct
'05
3:58 a.m.
On 24/10/2005, at 7:20 PM, Johnny Billquist wrote:
There basically isn't any (hardware, that is).
The 11/782 was not an SMP design. It was two CPUs with shared memory,
where one CPU acted as a slave to the other. All I/O was on the
primary
CPU as well. The second CPU was just a computing resource.
I haven't (yet) found any references to any interconnect hardware
apart
from the dual-ported memory boxes.
As far as I can recall, that's all you need (apart from a couple of
working 11/780s). The shared memory cabinet contained 4Mb of multi-
port memory. Two were used for the 11/782 but I think there were four
ports altogether. MA780 is the part number that springs to mind but
MA782 makes more sense :-)
Maybe someone else knows some more details?
Treat all comments as being restored from a nearly 20 year old 1/2"
tape with no error checking or correction.
Appearantly, it wasn't much faster than a normal
11/780 either, so
some of
the machines appearantly got split up into two separate 11/780s
instead.
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".
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 :-)
Huw Davies | e-mail: Huw.Davies at kerberos.davies.net.au
Melbourne | "If soccer was meant to be played in the
Australia | air, the sky would be painted green"