PDP-11 Newbie Alert --- (gotta start somewhere)

[Allison J Parent]

<> QBUS 11/2 11/03 11/23 11/53 11/73 11/83

<> (They're also old and will eat you out of house and home with their app
<> for electricity. :) 

None the above systems are tough it really depends on the disks used.  The 
later of the three in the microPDP-11 format (ba23/123) are very resonable 
using MSCP and MFM drives.  The QBUS-11s are modest power compared to the 
Ubus-11s.

Also the Qbus-11s win in the small sizing as well.  I have two BA11n boxen 
one with 11/23b and the other 11/73, RX02, RL02, and MSCP disks all in one
50" rack.

<For the sake of discussion, what sorts of power requirements would be
<required for a lowend version 7 or 2.11 BSD box?  Say that I wanted
<a machine that would allow me to troff/Tex a little, and do some
<minor C compiling, associated with that.

A qbus 11/73 (or 83)  a meg of ram and disks would be comfortably under 
500 watts.  Adding an RL02 is not painful though it uses more than the 
CPU box total.  The massbus disks or RK/RMs are high power just for the 
spindle motors.

<> Has anyone looked at the possibility of retrofitting older pdp11's with
<> switching power supplies to ease the electricity demands...?  

You could if you set up event, ACOK and DCOK.  Most of the DEC supplies 
are actually lowvoltage switchers (744s) and the later ones are high 
voltage swicthers (BA11s/BA32/BA123... all qbus).

<Are there special electrical requirements?  I can always find a separate
<20 or 30 amp 115 volt circuit, but the 220 lines are tied up in my
<antique radio transmitters.  Just how hungry are these pdp11s?

The bigger Ubus machines and some of the bigger (physically too) disks
are killer though most common PDP11s are really quite moderate to small in 
their needs.

<I consider it great fun to resurrect the old dinosaurs.  I still keep
<a few 8 inch CP/M S-100 boxes running, for fun.  Alas, finding parts is

Smae here, the CCS2200 with DISCUS 10m and two SA800s challenge the 11/23
for power needed!

<What exactly were the Heathkit things in relation to the mainstream pdp11
<There was a unix that was available on the Heathkit boxes, but I never di
<get enough money together at the time to get one --- had to settle for th
<CP/M thingie, instead.

The H11 was a LSI11/03 cpu with heath equivelents for DLs and memorys, the 
disks however were strange.

<What would BSD be comfy with, with a little space for play.  I remember
<the old Xenix boxes that we had (RS 16B things) ran a sort of v7 in abou
<15 megs HD.  The FreeBSD things require 100 or so megs to come up.
<What sizes of HD would one be looking out for, in the surplus piles?

I ahve V7 up on an 11/73 on one RL02 pack (10mb) and it's cramped with 
about 4mb free.  Two RL02s would be pretty good.  If I can get 2.11 up
that will talk to the MSCP disks RD52(31mb)/53(71mb) and I'd expect plenty 
of space then.

Allison


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