Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!zephyr!tektronix!psueea!parsely!sopwith!snoopy
From: snoopy@sopwith.UUCP (Snoopy)
Newsgroups: comp.arch
Subject: Re: Writable instruction set cpus
Keywords: cpu, 3b20d
Message-ID: <214@sopwith.UUCP>
Date: 5 Jun 89 00:27:24 GMT
References: <483@ntvax.UUCP>
Reply-To: snoopy@sopwith.UUCP (Snoopy)
Distribution: na
Organization: The Daisy Hill Puppy Farm
Lines: 48

In article <483@ntvax.UUCP> yang1@ntvax.UUCP (cqyang class) writes:

|  Is there anyone out there that has used an AT&T 3B20D minicomputer?

Yes.  Don't remind me.

| It is used by the telephone company to run with its 5ESS phone switching
| machines.

Yes.  The Duplex feature is very important for such high-rel applications.

| When running with the 5ESS, it uses an operating system called DMERT.

Duplex-<something>-Executive-Real-Time.  Something like that.
I believe they changed the name to UNIX RTR a few years ago.

| The computer system can also be used as a reliable stand alone
| minicomputer. It has two processor boards.

Two boards?  More like two racks-full.  A lot of the boards had their own
local micro (8085/8086/2911/etc) to do whatever.  A processor full of
processors.  (This was before divestiture, so you couldn't call it a "computer".)

| It constantly monitors itself to check for faults. When one
| is detected, a second processor board takes over, signals a fault, then takes
| off where the first processor left. The faulty processor board, or any
| other type of board that needs to be replaced, can be done while the machine
| is still running.

It also runs off of 48VDC batteries which are constantly trickle-charged.
If commercial power goes away the diesel generator is supposed to start up
before the batteries die.   Anything requiring AC (fans, disks) runs off an
inverter.  These inverters make for some great war stories.  *grin*

| Software upgrades can also be done while the machine runs.

Of course!  You don't want to pull the plug on thousands of phone calls
just to install a bugfix or the latest speed-forwarding feature, do you?
And you can back them out again if you decide the cure is worse than the
disease.

    _____     						  .-----.
   /_____\    Snoopy					./  RIP	 \.
  /_______\   qiclab!sopwith!snoopy			|  	  |
    |___|     parsely!sopwith!snoopy			| tekecs  |
    |___|     sun!nosun!illian!sopwith!snoopy		|_________|

		"I *was* the next man!"  -Indy