BBS software for the PDP 11

allison allisonportable at
Fri May 19 11:07:22 CDT 2017

On 05/19/2017 07:49 AM, Liam Proven via cctalk wrote:
> On 19 May 2017 at 13:36, Bill Gunshannon <bill.gunshannon at> wrote:
>> Nope. Take a trip to Amazon and look at just how much power this stuff
>> actually consumes.  And, if you go back to the days when we started
>> running this stuff in our homes, compare the draw of a QBUS PDP-11 to
>> a TV with a picture tube, standard incandescent lights, a refridgerator,
>> window air conditioners, etc.  Our toys draw much less power than most
>> people think.  Heck, I have seen modern PC's (you  know, the kind gamers
>> use) that draw more power and are frequently run 24/7.
Running a BBS I can think of several machines that re power frugal in the
DEC realm alone. 

Vt180 it a Vt100 power needs plus maybe 80W for the VT180 board and
four Floppies.   The total is under 120W based on an old measurement.

A PDP-11 Qbus machine with a 11/23 cpu and a RL02 or a RQDX/Hard disk 
was enough for running TSX and a few people timeshare in an office then
a BBS with one modem would be under utilized.  

A microVAX3100/20 with two 420MB disks would do that easy at under

Remember a BBS with 1 modem is runnnning at less (back then) than
1200 baud (120CPS!).  Name one CPU that can't grab one byte and
act on  it in 8.333mS?  The rest is enough storage to do a useful library
(download and upload programs, and some form of mail and forum/board).

> I wonder if this is one of those USA-vs-Rest-of-world differences.

Likely and also time frame.  PDP-11s had their peak life just like PDP-8s
and VAXen. 

> I think I have seen a running PDP-11 twice in my life, and it was the
> same one -- a machine I had to get exchanging files with Mac clients
> acting as terminal emulators, in about 1989 in my first job. It was
> already very old kit by then. I've no idea how much power they draw.
The power draw from from the micro level to the monster level.
For example a PDP11/150 was desktop and it plus the VT100 was maybe
150W, the 11/70 with a few RK07s and RM disks likely reuired a 230V 30A
line or more.

Most of the Qbus 11s (LSI-11 though 11/73) in single BA11 or BA23 box
were in the sub 300 W range as that was the limit of the power supply.
The disks for them could be PC class (early 80s) 5.25"  or RL02 and RX02.

My rack system with RX02, rl02, RD52x2 and 4mb ram and 11/73 cpu is
under 420W(460 with VT330) at 120V.    My former towerbox Xeon4/3ghz
with 4g of ram and a 160gb disk ran at 220W (24/7) the LCD added another
55W as a comparison.

I fired up the MicroPDP11 with a 11/23+ and 4mb ram, RD52 and floppy
and a VT320 and the KillaWatt was under 215W for the pair.

For comparison, my current desktop is a Mintbox and its maybe under
full load 12W (with usb keyboard and mouse).  The display dwarfs it.

> Window air conditioners are another thing I've never seen,
> incandescent lights are now a rarity in Europe, hoarded by some
> old-timers -- i.e. older than me, at a hair under 50. I've never
> bought a new TV set with a CRT, either. In fact most of my CRT
> monitors over my whole home computing time period -- nearly 40y --
> were cast-offs, hand-me-downs, or bought 2nd hand.
Led lights, an early adopter as I'm cheap(frugal) so between replacement
cost, heat load in the summer, and power consumption LEDs are cheap. 
I use incandescent for the times when color temperature is important
and LEDs can't cut it.

Then again I power my ham station off grid with 400W of solar and
150Ah of NiCd (industrial) battery.

CRT monitors I still have a few and one TV as its rarely used but
excellent quality.  I use terminals like Vt100, Vt180, Vt320 and even
VT1200 based on need or convenience.

By doing that I have the luxury of powering things like older computers
off of savings.

> I've bought a few 2nd hand LCD monitors now, because I like big ones.
> (Oo er missus, etc.) I'm currently running a 23" + a 24" on a 2011 Mac
> mini with a 1987 Apple Extended keyboard. All bought used. New kit is
> for suckers.
If you can buy it its obsolete, by used or cheap.  Also used is a good deal
by time one buys it the reliability of that model is known.

> So I don't look into power consumption -- used price is more important
> to me, TBH. Probably bad of me, but wotthehell archie wotthehell.

More information about the cctalk mailing list