Info-3b2 Digest, Number 15
Info-3b2 Mailing List
info-3b2 at lamc
Sat Sep 17 07:46:22 AEST 1988
Info-3b2 Digest, Number 15
Friday, September 16th 1988
Today's Topics:
Parts is Part(third try)
Re: 3B20
Re: Parts is Part(third try)
3B20 (Was Re: Parts is Part(third try))
----------------------------------------------------------------------
Date: 15 Sep 88 09:03:51 EDT (Thu)
From: grs at alobar.ATT.COM (Gregg Siegfried)
>From vsi!friedl Wed Sep 14 19:13:56 1988:
>It is my understanding that the 3B20 is done with bit-slice (AMD 2900?)
>and it not entirely compatible with the other 3B machines.
There are a few differences between the 3B20s and the other members of
the family, but all 3Bs profess to using the IS25 instruction set, and
with minor differences, they are exactly the same. I believe the opcodes
are a little different, though, so compiled code can't be moved from a
2 to a 20 in the same manner that code can be moved from 15s to 2s and
5s etc.
I haven't done extensive assembly language programming on the 3B line,
as C, of course, tends to do exactly what I want. I've read a good
deal of assembly though, and frequently check to see what the
compiler has generated for me.
>From a hardware point of view, they are very very different.. The
20 doesn't use the WE32000 chip, it has a CPU made up of different
boards, like the VAX 780s did, before VLSI technology allowed
people to manufacture wildly complex CISC microprocessors such as
the WE32000 and MC68000 et. al.
But, I'm a software person. Take that with a grain or two.
BTW .. I've gotten to use my first 3B2/700 this week. It's soooo
nice. If you have the means, I highly recommend it.
(with apologies to ferris beuler (sic):-)
Enjoy,
Gregg Siegfried
grs at alobar.att.com
------------------------------
Date: Wed, 14 Sep 88 09:29:55 CDT
From: lll-tis!ames!uwvax!shorty.cs.wisc.edu!sadler (Jon B. Sadler)
Subject: Parts is Part(third try)
The 3b20 does have uses other than doing line use accounting with the 5ESS.
(Yes, if the '20 goes down, your long distance call that goes through on the
Switch does not get billed to you! :^) This machine can run UNIX, and I
know that UIUC (University of Illinois - Urbana Champagne) has a few. One is
being used as the Midwestern HUB for the University Unix Users Group. As for
the others, I do not know.
Just a few bits of trivia on the 3b20:
- The original 3B20's had recoil starters. Before powering up the ma-
chine, it was necessary to pull the starter cord, charging up capa-
citors in the power supply, and avoiding a power surge that would blow
out components.
- The 3B20 allows you to take out boards, while the machine is up an
running -- just like the 5ESS. Why? This was done to help keep
machine down time low. Because (as stated above) when the machine
is down, call accounting on the 5ESS is not being done!
Jonathan Sadler
------------------------------
Date: Fri Sep 16 9:59:01 EDT 1988
Subject: Re: 3B20
From: netsys!cucstud!eawa2!ean6cc1!wpeace
The 3B20 line of processors are only source code compatible with the 3B2
family.
Although both families do use the IS25 instruction set, the implementation on
the 3B2 was changed to a certain degree.
------------------------------
Subject: Re: Parts is Part(third try)
From: netsys!att!looney!cmv
Adding to the 3b20 trivia that Jonathan started:
- The backup power for the 3b20s was a series of about six truck
batteries that sat in one of the cabinets. These would
keep power to the boards, which would patiently wait until
the hard drives came back up, and continue on where they left
off. I've seen it actually work a couple of times too!
- (This is the one we got the biggest kick out of) It seems that
in engineering this thing, the decision was made to have
an indicator for when there was no power. What came out
was an indicator lamp that lights up, when there's no power.
WHAT A COUNTRY!!!
-Craig Votava
------------------------------
Subject: 3B20 (Was Re: Parts is Part(third try))
From: netsys!att!ihlpb!dritchey
I just couldn't let this one go by.
>From shorty.cs.wisc.edu!sadler Thu Sep 15 18:41:43 1988
>Date: Wed, 14 Sep 88 09:29:55 CDT
>Message-Id: <8809141429.AA27893 at shorty.cs.wisc.edu>
>To: lamc!info-3b2
>In-Reply-To: Info-3b2 Mailer's message of 14 Sep 88 05:43:37 PDT (Wed) <8809140543.AA05712 at lamc.UUCP>
>Subject: Parts is Part(third try)
>
>The 3b20 does have uses other than doing line use accounting with the 5ESS.
>(Yes, if the '20 goes down, your long distance call that goes through on the
>Switch does not get billed to you! :^) This machine can run UNIX, and I
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Not necessarily true. See below.
>know that UIUC (University of Illinois - Urbana Champagne) has a few. One is
>being used as the Midwestern HUB for the University Unix Users Group. As for
>the others, I do not know.
>
>Just a few bits of trivia on the 3b20:
> - The original 3B20's had recoil starters. Before powering up the ma-
> chine, it was necessary to pull the starter cord, charging up capa-
> citors in the power supply, and avoiding a power surge that would blow
> out components.
Interesting story, but take with a large grain of salt.
> - The 3B20 allows you to take out boards, while the machine is up an
> running -- just like the 5ESS. Why? This was done to help keep
> machine down time low. Because (as stated above) when the machine
> is down, call accounting on the 5ESS is not being done!
>
>Jonathan Sadler
Yes the AM does have very low downtime (measured in seconds per
year). The specified downtime for AT&T Switches is listed as 2 hours in
40 years. Whether that is annecdotal or published, I don't know, but
that is the figure we hear used as a target.
The 3B20 computer on the 5ESS(*) Switch is known as the Administrative
Module (or AM) and does much, much more than call accounting on the
5ESS Switch. It provided all human access to the switch functions
(through terminals) and provides all the external world connections for
the switch. All control terminals, status printers, network control
center links, etc. terminate on the AM and are controlled (from the
UNIX(*) process perspective) by the AM. The AM also performs much of
the global routing of calls on the 5ESS Switch for calls to trunks and
calls to multi-line hunt groups that may appear on more then one
Switching Module (or SM).
Contrary to the above, when the AM is down, the call accounting does
continue, because the SMs do call accounting. However, the centralized
collection and logging of the calls occurs in the AM, so after a while,
the Automatic Message Accounting (AMA) record buffers in the SMs would
overflow and then some call accounting records would be lost. But that
takes a while. In the meantime, the switch would have more serious
problems than the loss of a few AMA records, since trunk calls and some
other calls would fail. From a Telco perspective, that is more
serious.
Yes, you may pull circuit packs from a running 5ESS AM and not affect
the switch, but that is because the AM and SMs are fully redundant in
the critical resource areas. For more details, see the published
literature in the AT&T technical publications on the 5ESS.
Yes, the 3b20 is an interesting beastie, but lets get back to the
business at hand, the 3b2 family of computers.
(*) 5ESS and UNIX are registered trademarks of AT&T.
Don --
Don Ritchey (312) 979-6179 IH 2F-416
ihlpb!dritchey AT&T Bell Laboratories, Indian Hill
-------------------------------------
To join this group or have your thoughts in the next issue, please
send electronic mail to Ken Davis at the following address;
{pacbell,netsys,hoptoad,well}!lamc!info-3b2-request
The views expressed in Info-3b2 Digest are those of the
individual authors only.
*********************
End of Info-3b2 Digest
*********************
More information about the Comp.sys.att
mailing list