11 Apr
2013
11 Apr
'13
3:49 p.m.
On Apr 10, 2013, at 2:25 AM, Arno Kletzander <Arno_1983 at gmx.de> wrote:
That's a fun idea. When I'm running my 11/23 in an open backplane,
I make sure I have a decently powerful fan blowing through it and
over the top. Those boards tend to dissipate between 10 and 20
watts each, which is nothing to sneeze at, and the CPUs can get
quite locally hot.
ok, then TU58 emulation is, as I had hoped, going to
float the boat for me, at least until either more machines or media to be read crop up
here.
If you manage to find a QBUS SCSI card (I have the CMD CQD-220, which
I like a lot), you can use a Zip drive for removable storage (or even
primary storage, though having done that for a bit I'm not sure I like
the idea of torturing the disks like that). It's not exactly "classic",
but they are plentiful and cheap and fairly reliable if you stick with
the 100 MB versions. They're also BIG (in storage size) compared to
an RL02, and they're much better about being dropped. :-)
Unfortunately I have no sound way to (mechanically)
_mount_ and power those tiny little 5,25" disks in the '11 rack, that's why
they're staying in the BA123.
I forgot the 300MB ESDI disk I got from a listmember together with a Webster Qbus
controller, I'll use that one if I ever want to run a large OS on the VSII.
You could always run your -11 from the BA123. It's a bit of overkill,
but you can fit all the disks you want in there and pretty much never
worry about running out of slots for boards.
Of course, if you're actively using the MVII, don't do that.
One last
thing...
Heat! Qbus 11s produce a bit of that. That means fans must all work,
the location must not be dusty enough to load up the boards and local
temperature not excessively hot.
I fried a 11/23 board while working at the DEC Mill when they had an air
conditioner fail for the office area, when the room hit 96 (36c), cpu
went away, I had plenty of spares. So reliability and room temps are
coupled. Qbus 11s are fairly tolerent of conditions but any you find
are going to be old and may not like additional stress.
A hard "CPU dead" damage without any warning? That's bad.
Good to know anyway, makes me want to add a system monitoring function
(temp and air flow) for emergency shutdown. Maybe something to design
a CD slot board for after all ;), at least before I'll run the machine
unattended. I also forgot something: I myself wouldn't have
thought of putting a NIC
(DEQNA or similar) in a pdp-11, probably just for the notion that back
in those days, computers were too few and far between to come up with the
concept of a Local Area Network. Obviously I was mistaken here, too.
The QBUS LAN cards definitely have more of a "meant for VAX" feel
to their documentation, IMO, but they do work fine in an -11.
If you can find a DECNET distribution, you can usually even get
the drivers for them running on a DEC OS as well! TCP/IP is
somewhat rare, though, because the stack takes up so much room.
I know Johnny Billquist mentioned that he had at least UDP
running on RSX-11M+; I can't find the email now, so I can't
remember about TCP. There are commercial TCP/UDP stacks for
the DEC operating systems as well.
If you can, I'd recommend getting a DELQA instead of a DEQNA.
The DELQA is backwards-compatible with the DEQNA and is a lot
more reliable (mostly due to lower power dissipation). I'm
given to understand it takes a lot of load off the CPU as well.
The DELQA can use the DEQNA cable kit, so no need to worry
about that.
- Dave