2 Jul
2018
2 Jul
'18
3:56 p.m.
I have several working 3B2s and a non-working 3B1 aka UNIX PC/ 7300.
Your story sounds more like a 3B1 where Convergent Technologies was
the ODM (original design mfg). I've seen Convergent branded 7300s in
collections or for sale.
The various 3b2 models are a relatively simple backplane design, the
cards are all discrete chips on small boards that aren't very dense
integration vs other contemporary systems. I couldn't see more than a
few manual reworks being more cost effective than reving the PCBs on
it, especially because it was a "serious system".
Wikimedia has a good pic of the first model, 3B2-300, main board
https://upload.wikimedia.org/wikipedia/commons/3/3d/3b2-300-motherboard.jpg
One thing I've desired are contemporary pictures of the 3B5, 3B15 and
3B20 if anyone knows of intact machines.
On Sun, Jul 1, 2018 at 6:29 AM, Steve Johnson <scj(a)yaccman.com> wrote:
The 3B2 was designed for AT&T by Convergent
Technologies. I later worked
with several people at Convergent, one of whom had a framed circuit board on
his wall. It was a wonder to behold -- the board had wires all over it that
were added later, and nearly a dozen "bugs" -- in the days of discrete logic
chips, a bug was when you took another chip and glued it, upside down, on
top of an existing chip and then ran wires to the pins in the air. As I
recall, the story was that the first demo of the 3B2 happened roughly six
weeks after the initial request, using the board on the wall. Now, that's
what should really be in the computer museums...
In those days, if there was floating point it was a separate chip, and the
3B2 had none. Floating-point instructions caused a fault, which meant a
context switch to the OS, where the instruction was emulated and then the
program returned. The performance, as I recall was about 800 FLOPS -
dismal. We fixed the compiler so it would generate calls to subroutines
that did the floating point operations, and the performance improved by over
an order of magnitude -- still dismal, but no longer ridiculous...
One of the events that led me to leave AT&T was that they fired the head of
the benchmarking group at Indian Hill, a most competent woman, because they
didn't like the results she was presenting. When a company's information
channels stop functioning reliably, it's time to leave...
Steve
----- Original Message -----
From:
"Doug McIlroy" <doug(a)cs.dartmouth.edu>
To:
<tuhs(a)tuhs.org>
Cc:
Sent:
Sat, 30 Jun 2018 14:24:24 -0400
Subject:
Re: [TUHS] AT&T Hardware
Anent 3B's: Last time I visited Paul Allen's Living Computer Museum
the only working Unix on display was running on a 3B2. Apparently
the machine was robust if nothing else.
doug