15 Oct
2007
15 Oct
'07
5:04 p.m.
On Mon, 15 Oct 2007, Tony Duell wrote:
Personally, I theink the 11/750 is not the best machine to try to keep
running. The reason is that the CPU is made up of a large-ish number of
custom gate array chips. Even when they were available as spares from DEC
they were very expensive, now they're unobtainanle other than by raiding
other 750s.
If you have the space (and it's large), try to get am 11/780. I've never
been inside one, but I've read the printset (schematics) and it seems to
be all standard chips.
If you don't have the spave, and can stand the lack of speed, consider an
11/730. It's small (1 10.5" high rackmount unit), you can fit the
processor, disk and tape drives into a half-height rack (this was a
standard configuration). It's almost all standard chips, 2901 ALUs, TTL,
non-protected PALs, etc.
-tony
I like the 750. It can be plugged into a 30A 150V outlet without any
problems. It isn't as fast as the 780, but you can rebuild 4.3BSD from
sources in about 10 hours. I have a goal to decap the gate arrays and take
die photographs, but haven't done so yet.
The 780 wants 3 phase power, but you can jury rig the supply box
to run on 2 phase with an external supply for the air flow sensors. It
generates a LOT of heat, so running without airconditioning is a sure path
to hardware failure.
730's are dog slow. I'd take a uVax or VS3100 over a 730 except for
curiousity sake. Unfortunately, many were cannabalized for the 2901's to
repair video games, and the PALs are hard to find anymore. The printsets
also appear to have errors (delibrate?) with regards to the PAL fusemaps.
I got a second one to reconcile the errors (Thanks Emanuel!), but haven't
had time to do so.
Clint
So you want me to start off with a VAX?
Lots of folks on this list have lots of nice things to say about the 11/750.