13 Feb
2013
13 Feb
'13
5:12 p.m.
On 2013-02-13 16:09, Clem Cole wrote:
On Tue, Feb 12, 2013 at 8:08 PM, Johnny Billquist <bqt at softjar.se
<mailto:bqt at softjar.se>> wrote:
Well, the 11/70 easily outlived the 11/44, in that 11/70 machines
were still sold after the 11/44 was terminated, as far as I know.
Interesting data. I'm a little surprised to hear it because DEC was
clearly trying to get the traditional 11/70 customer to move to the VAX
line in those days.
Oh, DEC tried. It was just that the VAXen didn't deliver the goods for all customers.
The real pain point was realtime stuff. Interrupt latencies on a VAX is horrible compared
to a PDP-11. And VMS don't help.
Fun detail: when devices want to MOP boot on a network where you have both a VAX and a
PDP-11, the PDP-11 normally ends up serving the image, since it responds much faster than
the VAX.
This has been observed with a PDP-11/93 on the same network as a VAX 4000-96 (if I
remember the designation right).
I wonder if the 70 was used in some commercial
settings where they wanted a real duplicate.
No. The 11/70 just delivered more punch than an 11/44, so once the people who just liked
the size or cost of the 11/44 had been satisfied, why would anyone buy it? The 11/70 still
existed, and delivered more performance.
In reality, the 11/70 gave the most bang, until the 11/9x machines were introduced. And
for many, money was less of an issue than performance. Especially as times go by, people
want faster machines. Thus also the third party PDP-11 manufacturers who offer even faster
PDP-11s, even to this day.
DEC, in its infinite wisdom decided to not make any faster PDP-11s after the 11/70, but
instead tried to push those customers to the VAX. The PDP-11 is still in service in many
places. Guess DECs strategy didn't work. Customers wanted PDP-11s for other reasons
than DEC thought.
DEC let the PDP-11 live as a niche product for small realtime use, where they did
recognize that the VAX just could not compete because of price. But faster and larger
PDP-11 models would have cut into their VAX business, and thus it did not happen, even
though customers wanted.
Unlike the Nova/Esclipe
the VAX had a "compatibility mode" but it was a tad impure. The OS was
different and binaries did not work with some assistance. Other than
running Dungeon and few other games, I never knew a customer that used
compatibility mode in production - it was a great sales tools, but once
folks got their VAX they tended to do a "full port" of the code. So
swapping a VAX besides costing more, meant some systems/SW work on the
customers part. That was not true of the 11/44.
The compatibility mode was used extensively in the early days. At VMS V1, almost
everything was running in compatibility mode. You used almost all RSX cusps, all RSX
language compilers, and so on.
Native VAX was the kernel, RMS, MACRO-32, LINK, DCL and the replacement for PIP. MACRO-11
and TKB was used for most other stuff.
It wasn't until VMS V4 before most traces of RSX had disappeared. The one exception
still at that time was TECO. TECO was eventually made native as well, but that took time
(TECO eventually also got a callable interface in VMS, but that was even later.)
Yes, the PDP-11 emulation in the VAX was incomplete in that it only emulated at user mode,
and without things like split I/D-space. But within its constraints it worked without
problems. Which is why plain RSX binaries runs just fine on VMS.
I remember buying an 11/44 for use where we did not need (could not
afford an VAX for that use) but wanted the larger address space over the
40 class machines. We had a very large 11/70 and were also buying Vaxen
at the time,
Larger address space than an 11/40 is understandable. The 11/44 was more compact than an
11/70. But slower.
That particular machine was the last 11 I ever personally was part of
the purchase and I moved on to other things, so I sort of stopped
watching the progress of the PDP11 line. I know the QBUS gave the 11
some amount of resurgence, although by then most of us were using Vaxen
or 68K based UNIX boxes.
2BSD was rather actively maintained until only a few years ago. I should try contacting
Steven Schultz again about my latest set of patches... Do you know what he is up to right
now?
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic
trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" -
B. Idol