information about the PDP-11/68 (also for PDP-11 FAQ: The Never 11's)

[Johnny Billquist]

On 9 Date: Sat, 7 Oct 2006 18:00:13 -0400 "Bill Pechter" 
<pechter at gmail.com> wrote:

 > I believe the 11/68 was known as the Bluefin and was cancelled fairly
 > early on before it was out of prototype. I think Ontario Hydro was the
 > place that got the 11/74's. I never heard of AT&T having them. My wife
 > was in AT&T, Bell Labs and Bellcore and she never heard of one of them
 > there.

This is urban myth appearantly. No 11/74 systems were left at customers 
at the end of the field tests.
The most common myth is that Ontario Hydro whould have kept one, but 
sources there have denied it. Another myth about Ontario that I've read 
were about when DEC tried to convince them to change their 11/70 systems 
(or if it was disks) because the money they would save from lower power 
consuption of another system, which were replied to with a "maybe you 
didn't hear where I come from...". I think that actually may have been a 
DECUS Q&A session... And that one might be true. I don't know...

Anyhow, back to the 11/74 systems... No, I remember (and probably still 
have the mail somewhere) that persons within Ontario denied that they 
kept any 11/74 systems. Also, people within DEC have firmly stated that 
all 11/74 systems *were* returned.

 > The last of the 11/74 KB11-CM cpus were used internal at DEC when they
 > had to ship a ton of refurb 11/70's to AT&T. (they were out of
 > production and wouldn't meet the FCC regs... so DEC called in a bunch
 > of their 11/70 systems from Software Development and Field Service and
 > shipped the newer cpu's from the 11/74 project to them as a
 > replacement.

Well, it is true that DEC shipped KB11-CM cards to customers to use in 
11/70 systems, but that wasn't the last of it. DEC still had/have 
working 11/74 systems in house, and in the early 90s they did a 
corporate wide search for 11/74 components, I believe, to keep their 
systems running. (Memory a bit hazy now...)

When DEC disbanded the PDP-11 OS groups, the RSX team's 11/74 (CASTOR::) 
were moved to Colorado Springs. The DECnet group's 11/74 (just 2 cpus, 
POLLUX::) were also there, and FS took over the system. Well, actually 
Mentec took over the system, and kept it running for another number of 
years. As far as I know, the system they have still exist, but last I 
heard they had some hardware problem with the machine, so it wasn't 
functional. This was maybe four years ago.
Also, RSX development have finally moved off the 11/74 onto something 
faster. But until recent emulators on really fast hardware, the 11/74 
was still the best workhorse for the development system. Which is why 
RSX have a very nice and functional MP implementation. :)

However, appearantly the physical machine stayed inside DEC, then 
Compaq, and I would expect currently HP. And it sounds like there is 
little chance of the machine ever leaving the premises. If it is 
disbanded, it's destined for the scrap heap. Or atleast that's what I've 
been told. If someone ever manage to get it out of there, I would love 
to help it back to running order.

 > We got one at DEC Princeton around 83 or so... Just different enough
 > to require separate not-too-available spares. They were used for a
 > short time with RSTS/E until the internal stuff moved to VAX/VMS.

I would think that most components would be the same as the 11/70. 
Looking at the module list, only a few modules differ.
Analysing it, the changes would be in the memory bus interface (that 
means both cache modules and memory box bus interface). Second, the MMU 
and ASRB microcode is changed. But I believe that's it.

 > There also was a system called Unicorn (which I think was another
 > extended 11 prototype which was the development of the VAX SBI bus and
 > MA780 memory -- later used in the VAX but built before that.

That would be interesting to learn anything more about.

Of course I assume you know that the PDP-11/70 and VAX-11/750 use the 
same memory bus, and same memory cards (with a few restrictions).

	Johnny