AT&T 3B2 400 emulated

This is super awesome!


Memory size: 4 Megabytes
System Peripherals:

Device Name Subdevices Extended Subdevices

Floppy Disk
72 Megabyte Disk

This machine has to be set up by you. When you see the "login" message type
followed by the RETURN key. This will start a procedure that leads you through
those things that should be done the "first time" the machine is used.

The system is ready.

Console Login:

Back in the 1980’s AT&T shifted UNIX from being an internal research project that got somewhat popular in college spaces (and larger companies, General Motors was an early UNIX adapter, along with companies like Industrial Light and Magic).  Quickly after the divestiture of 1984, AT&T entered the commercial space with it’s own custom machines & their home made UNIX operating system.  Below is one of the ads they ran in 1984, touting their so called ‘super microcomputers’, featuring the 3B2, the 3B5, and the AT&T Personal Computer.

Thew new computers from AT&T

And indeed for many a government institute bewildered by the dozens of UNIX vendors, standards, and chaos of different platforms and processors many were all to happy to buy AT&T UNIX on AT&T machines.

And indeed this was my first experience with genuine SYSV Unix.

And I hated it.

Initially I had been thrown at an English computer lab because I knew how logon and do my work in style & diction, they decided I could help.  The system was aging and had major problems, as some prior students had figured out enough of the link kit that they would put their own attempts at re-writing portions of the kernel into the system, and it’d break.  Naturally the original installation diskettes were lost, and the best that could be done was basically shut it down throughout the day and run the disk repair utilities.  It was not a fun job.

Later on the 3B2’s were thrown into the ‘common garbage’ aka free kit for other departments, and the 3B2’s re-appeared at the next place I was volunteering at on campus.  However in addition to the two machines, there was a few other boxes of manuals, and oddly enough the installation diskettes.  And also about a dozen of these AT&T ISA Starlan adapters.  These weren’t the ones that were basically Ethernet (Starlan10) but rather the original ones.

Through some incredible luck we did find an NDIS 3 MS-DOS driver for the Starlan car, and we were able to cobble together a Starlan1 LAN consisting of a 3B2 that we cannibalized the RAM and disks from one of them to make a ‘super’ 3B2, with added TCP/IP software and a massively cut down port I did of samba to turn it into a tiny file & print server (72MB MFM disks were it’s biggest if I recall), along with Windows 95 clients.  And of course with a TCP/IP lan we could easily load a proxy server (WinGate?) on one machine with the 56kb modem, and now we all had internet access.  I know it’s sad today, but trust me back then it was “a big deal” that we had a fully functional LAN.

Over on there is an incredible amount of information about the reverse engineered WE32100, along with the 3B2 hardware, and of course information about the newest SIMH simulator the 3B2/400!

Instructions and disk images on the site made it incredibly easy to grab the latest SIMH Windows Development binaries, and get my own virtual 3B2 up and running in minutes! So naturally I pasted in dhrystone.c to see if it’d work.  And that was the first weird issue is that the backspace is the pound # key.  So all the C macro definitions lost their # sign.  I added them in vi without full terminal support because I’m crazy and:

# uname -a
unix unix 3.2 2 3B2
# ./dhrystone
Dhrystone(1.0) time for 500000 passes = 40
This machine benchmarks at 12500 dhrystones/second

Obviously this is 100% bogus, as the real machine should get around 735, and I didn’t even bother with the -O flag.

The current emulator doesn’t do any additional serial ports, nor any Ethernet adapters.  So you only get a console.  But with the pre-installed C compiler image, I was able to build a trivial file just fine.  Although pasting on the console really leaves a lot to be desired.

SDF AT&T 3B2/500 UNIX System

I know for some of us old people the 3B2 hid in the corners of our call centres, running our AT&T Definity switches, our voicemail, and even some of our early ISPs.  After funneling money into SUN to get them to work on SYSVr4 which was the grand unification of BSD + SYSV AT&T’s interest if UNIX quickly waned, and they divested themselves of UNIX, and eventually all PC hardware, although they did re-enter the PC space a few times before exiting yet again.

As time would tell, proprietary hardware + a previously ‘open’ operating system were not the winning combination.  And so far the only UNIX vendor to weather the Linux storm so far is IBM with it’s A/IX.

10 thoughts on “AT&T 3B2 400 emulated

    • People have been writing it as “IBM A/IX” as long as I can remember. Maybe it’s from version 2 when it was on the PS/2 to match OS/2, but I sure remember A/IX version 3 on the POWER 520 and it being called that. In version 4 it was more AiX, but I’m pretty sure if you check Usenet, and dated literature you’ll see it.

  1. Alas, it is the AT&T 3B1 to whom my heart belongs. Sadly, the work in progress 3B1 emulator hasn’t seen an update in years.

    • I took a stab a merging some of the CPU changes from a newer version of Musahi, and all I got was that there was an incredible amount of CPU hacking in that 3B1 emulator.

      • The CPU hacking was mostly to make the early version of Musashi that it uses support an MMU (it had the hooks to support one but they didn’t actually work right). The current versions of Musashi support MMUs, so it would probably be a good idea to merge it into MAME’s skeleton 3B1 driver (or at least use it as documentation to finish the driver). I should maybe try to do that. I contributed several fixes to the 3B1 emulator, getting it to the point where it would run Unix, although I haven’t contributed anything to MAME.

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