Original PDP-11/10 [was: Re: Origin of 'Straight 8' name]

Jay Jaeger cube1 at charter.net
Fri Dec 21 15:47:27 CST 2018

On 12/21/2018 3:07 PM, Paul Koning via cctalk wrote:
>> On Dec 21, 2018, at 3:06 PM, Bill Degnan via cctalk <cctalk at classiccmp.org> wrote:
>>> My _guess_ is that that probably happened because there is no formal
>>> 'model'
>>> for that first one (unlike the first -11, which got re-named the -11/20
>>> BITD), and people recently picked that to disambiguate them from all the
>>> other -8's.
>> The original PDP 11 was sold in two model options, although the numbers did
>> not appear on the faceplace, very clearly the model options were called PDP
>> 11/10 and PDP 11/20.  These are just as legitimate and well defined as the
>> 11/05 vs. 11/10 (later version) that followed it except for the one fact of
>> the front plate.  The fact that the name does not appear on the front panel
>> has caused every DEC historian to miss this factoid.  Read the first
>> brochure, don't take my word for it.
>> http://vintagecomputer.net/browse_thread.cfm?id=593
>> Momentum prevents change I get it, but it's clear that the model 11/20 and
>> 11/10 existed from day one.  The problem is that DEC re-used the 11/10
>> model name again a few years later, the other cause for neglecting the
>> original 11/10 model.
>> Bill
> Wow.
> Did that V1 11/10 ever ship?  Do any still exist?
> I'm curious about that 1 kW read-only memory.  What technology is that memory?  At that size and that date I suspect core rope, but that would be pretty expensive (due to the labor involved).
> 	paul

It shows up in the pdp11 handbook 1969 inside/1970 on the spine, and
pdp11 handbook 2nd edition (also 1969/1970), but has been displaced by
the latter 11/10 variant by 1972.

Perhaps, since the *only* difference was the memory configuration (near
as I can tell), there may have been so few orders (maybe even none?)
that they just dropped it.  Or maybe a marketing / design team
communication misstep.

The pdp11 handbook from 1969/1970 identifies the memory attributed to
the 11/10 only as read-only core memory with an access time of 500ns
(same as the RAM core).  It describes the tiny RAM for the 11/10 of 256
words has having a 2us cycle time vs. 1.2us for the 11/20.

The handbook also indicates that an 11/20 could do an NPR transfer every
1.2us but an 11/10 could do one ever 1.0us (probably assuming ROM cycle

As a guess, they may never have sold any (or delivered 11/20's to those
who ordered 11/10's).

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