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

[Bill Degnan]

On Fri, Dec 21, 2018 at 4:47 PM Jay Jaeger via cctalk <cctalk at classiccmp.org>
wrote:

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

When you consider the differences between the 11/35 and 11/40 were simply
option choices and the later 11/10 11/05, I can see no reason why the
"original 11/10 11/20 is any different other than the front plate being
"PDP-11" for the later pairing.  I am unaware of any 11/10's still around
but I am also unaware of any Rolm 1601's that still exist, does not mean it
was not a real Ruggednova model.  etc.

Basically it's being inconsistent to not acknowledge the original 11/10.

We could say that the PDP 11 models were
11/20
11/45
11/40
11/10

... and ignore the original 11/10, plus the 11/35 and 11/05.

I will still sleep well at night regardless what officialdom decides. :-)

Bill