PDP-8/E PSU Debugging (was Q-bus pinout)

From: Allison J Parent <allisonp_at_world.std.com>
Date: Fri Apr 9 23:32:06 1999

<Too bad it's wrong.

It misses a few details bit it is essentially correct. Do research before
you indite the document.

<It makes it seem as if there was a box that was designated PDP-8/E and it
<had a particular configuration that was retired until the introduction of
<new box with the designation of PDP-8/F. This isn't supported by the eviden

No. read the whole FAQ to get the full picture. that was an excerpt.

<What really happened, and I have several independent confirmations of same
<is that the PDP-8/E system evolved into the PDP-8/F in a series of steps.
<Depending on the date code the machine was configured differently.

Yes and sorta. the 8E was the large box and remained as the "big version".
As a cost moderating measure the smaller 8m/f versions were created for
more limited expansion and with a lower basic cost.

<The evolution vectors were as follows:
< Module updates - example M833 - M8330, M831 - > M8310

Bug fixes. early in the 8E life and nearly predating the later omnibus 8s.
The original designs had poor margins and too much green wire. Even later
ones have green wire.

< Chassis updates - Long box, single OMNI BUS
< Long box dual OMNI BUS

< Short box single OMNIBUS Linear PSU on side.
< Short box single OMNIBUS Switching PSU in
Rear version replaced the really broken side mounted PS version. The
switcher was not the best design as it was fairly new technology.


< Front Panel Updates: Diode logic + 8v LAMPS

Early 8Es only. Driven by manufacturability.

< TTL logic + 6v LAMPS

Bulk of production and the common verison in the 8E

< TTL logic + LEDs in lamp sockets

Never made, it was a field third party retrofit.

< TTL Logic + LEDS

8F/M pannel later in design than the 8e v2.

< PSU updates - Long linear PSU
< Short linear PSU
< Short Switching PSU (types A and B)

Not updates litereally differnt products with overlapping production lives
save for the two switchers.

<At some point in this evolution some marketroid decided to change the name
<from 8/e to 8/f. The OEM version of this platform was called the 8/m and

Sorry no! the 8E remained in production and the 8f was the short 20 slot
machine and aimed at lowering the cost for those that didn't need/want
38 slots.

<included an optional limited function front panel (although all 8/M's I've
<seen so far had the programmers panel but that's only about a dozen so who
<can say)

The 8M was a fairly standard menu machine with the limited function panel.
It's options included a full function pannel (if you were a volume customer
custom colors and board mixes).

<I happen to have an 8/e that is:
< Short box
< 6v LAMPs plus TTL front panel
< Side mount PSU

That is not an 8E, it a frankenmonster in a 8m crate.

<I recently picked up an 8/e chassis that had the dual OMNIBUS backplanes.

That is an 8E.

<It is this one that doesn't have a cover. It may have been mounted in a
<desk, I don't know (it also didn't have a front panel but I can use my
<other 8/E front panel with it)

The 8e was the model with the long linear PSU on the side and the dual
omnibusses.

<My guess is that the evolution of the 8/E was driven by the introduction o
<the 11/20 since these changes seem have occurred between 1970 and 1972. Al

No. the two were entirely differnet development and had the common thread
of newer low cost TTL available.

<8/E's with date codes prior to 1970 appear to be the diode front panel
<type, All 8/E's after 1972 appear to be either 8/F's or 8/Ms (until the 8/
<came out).

8Es were 1970 introduction. Parts will have datecodes up to a year older
than that.

<The 8/M and 8/F are primarily differentiated by different inserts/color
<schemes, electrically they appear to be identical. The solder mask of the
<front panel says "8/E"

The same pannel was used for all. It was an assembly level options that
set them apart.

Since parts were swapable there were a lot of variations due to parts being
moved as needed to maintain systems or make working ones.

The omnibus series of PDP-8s were all driven by lowering costs and product
improvements. Even the later 8As were KK8e cpus (m8330/8310/8320/8300).
The actual 8A CPU (kk8a?) was a hex module.

Allison
Received on Fri Apr 09 1999 - 23:32:06 BST

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