> On Sun, 7 Oct 2001, Dave McGuire wrote:
> 
> > On October 7, Anders Magnusson wrote:
> > > The 782 is in principle two 780's, each of them with separate IO devices,
> > > separate memory etc but with some shared memory (in a separate box) to
> > > make the two machines to be able to communicate with each other. The
> > > shared memory is intended only to send messages between the two machines,
> > > it's slow and normally very little memory. Its intended usage is something
> > > like the SYSVSHM that communicate between processes.
> > > 
> > > So, the 782 machine is just two "normal" single-CPU machines that can talk
> > > to each other faster than over network. I know Mach was ported to that type
> > > of VAXen but I think that was only for testing purposes to see if the Mach
> > > concept worked on it. It wouldn't be realistic to try to port NetBSD to it.
> > 
> >   Given that, it might be better to think of the 782 as a
> > "configuration" of two 780s with a shared memory option rather than a
> > separate model of VAX in its own right.
> 
> My memory is a bit fuzzy, but I'm not sure this is correct.
> 
> In the 11/782, you have two 11/780s with shared memory. But one of the
> systems acted as a slave to the other. All I/O was done through only one
> of the systems. The other was just a CPU resource.
> 
Hm, I had to check this in the "VAX Hardware Handbook" :-)

The "basic" 11/782 has a master CPU with 2 MBA, 1 UBA, 512KB local memory,
a MA780 with 256KB shared mem and a slave CPU without I/O adapters but
with 256K local mem.  The machine was easily expanded with I/O adapters on
the slave CPU and with more memory, both local and shared. It was also
sold as a "dual 11/780 system" where it had already been equipped with
I/O adapters on the slave, and just used the memory as a fast way to 
communicate. The 11/782 that smugglers were trying to get over to the
Soviet Union ~20 years ago were such machine; I was offered it some years
ago from FOA (the Swedish Defence research centre), and it was _very_
well equipped :-)

-- Ragge