> Thor Lancelot Simon wrote:
> 
	>I think you have the model numbers mixed up.  A 785 is a 780 with
an
	>upgraded processor board.  A 782 is two 780s connected by a
shared-memory

	This is all correct.

	>box.  Though I don't think they were ever officially cataloged, the
	>additional ports on the shared-memory box could be used to build
"783"
	>and "784" configurations and reportedly at least some of these were
in
	>fact shipped from the factory as that configuration and had actual
DEC
	>VAX 11/784" badges on them (there was one such at Ontario Hydro,
IIRC).

	I've never seen anything that suggested that there was
	ever a machine called the VAX-11/784 (or 783 or 787 etc.)
	There are plenty of web pages out there that claim that Mach 
	was developed on a 784 (amongst other things). But most of
	these pages are obviously copies of the "master" page and I
	don't see anything at all authoritative on those pages.

	There is a paper floating around that describes the
	steps some group went to to build their own
	multiprocessor VAX by disassembling a few 780s.
	I forget if they went the whole hog and put more than
	two cpus together.

	Note that even the handbooks show long
	"butterfly" configurations where bunches
	of VAXen are connected to sets of MA780s.
	These are not new machines - they are simply
	VAX-11/780s that share some common memory.
	They would run independent copies of their OS
	and simply coordinate access to the shared
	memory pool.

	I've heard stories of Ontario Hydro field testing
	the PDP-11/74 (a dual processor PDP that did
	exist but was never released). 

	>Architecturally this is a rather strange beast; not really like the
SMP
	>machines NetBSD currently runs on.  Support might be quite a bit of
work.

	It's asymmetric which is one of the reasons VMS
	dropped support for the VAX-11/782 once true
	SMP came along in V5.0.

	Antonio