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Thread: It's ALIVE (3B2-310 Fired up today...)

  1. #1

    Wink It's ALIVE (3B2-310 Fired up today...)

    Set myself up a proper work space today and, because someone mentioned it in another thread, picked my AT&T 3B2 as the first classic to get fired up.

    I have an XM expansion module lying about as well so figured I'd open that up, make sure no rats had made the thing their home, and plugged it in. There's no power switch to turn on...


    Looking at the back, there's two jacks labelled "power control." Not sure how this works since the 3B2 *does not* have the same plugs on it.


    Nothing happens, so on to the 3B2...

    Looking at the side cover, looks like I have 16x serial ports for terminals, 2x printers, and one other "card."


    Taking off the lid and peering inside...

    These two "slots" are full -are these memory expansion cards?

    Top view of 4x expansion slots. What is the card on the left? I see an AMD DMA chip but...?

    HD & FD:

    With no terminals lying about, I had to find my homemade cable from 20 years ago...


    ...but in one of the purges, I must have dumped all of my connectors / cables / etc. so the only computer with a 25 pin serial port is a Heathkit XT...
    Now that damn thing hasn't been turned on in 20 years but starts right up in DOS 6.22 and autoloads a terminal program automatically (LUCK!)

    Screens below here show the 3B2 passing it's diagnostics, but it also finds an error on the HD.


    Next screen shows the devices:


    And finally a login prompt...
    NOW WHAT? LOL...


    ================================================== ==================

    Some questions:
    1. I *do* have the System V disks (5 1/4" Floppies) and I *do* remember being able to "reset" the admin password with them, but forget how at the moment. I also don't want to ruin them either... Will keep looking and see if I can't just find the password written down on an old note card.
    2. The machine seems to "go to sleep" after 10 minutes or so of sitting idle. Normal?

    More to follow!

  2. #2
    Join Date
    Mar 2011
    Atlanta, GA, USA


    Do you still have the XM fiber interface card? I didn't think it was supported on v2 hardware. The DataKit card stack and ISN were more that era. I remember the first FXMs coming out in the late 522 and 1000 series v3 machines.

    I believe the "power control" ports were for an external hard drive enclosure.

    Yes the two side slot are for the main memory. I'm not sure what the CIO card is in the upper right. It should have a three digit CM code on it somewhere.

    If you need to reset the root password, boot from the first Essential Utilities disk, press the reset button during DIAGNOSTICS to drop into firmware mode, enter password 'mcp', boot /unix from floppy, type 'magic mode' at the restore prompt, then type 'shell'. You should be able to mount the root file system (/dev/dst/c1t1d0s0) and make changes. You can also do this with a floppy key diskette that was written by the same machine. But the former method is easier and more likely to succeed.

    If the 10 minute idle is just the screen blanking, that is a feature of the termcap. Was normal on AT&T terminals back in the day.
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  3. #3


    A 3B2 "XM" involving fiber is going to be something else. In the context of the /300 and /310, the XM is a box that holds a second hard drive and possibly a tape drive, since neither of these will fit in the base box. It connects via the standard ST412 type 34+20 pin IDC header arrangement, on a bulkhead panel (which also includes a jack for the power sequencer) out the back of the system unit.

    I'd kinda like to find one, actually, my /300 is kitted out for it.

  4. #4
    Join Date
    Mar 2011
    Atlanta, GA, USA


    Ah, I was thinking of the Fiber Expansion Module (FXM) that came out late in the 3B2 world. It was a single card (unlike the DataKit) that had two fiber ports - one for receive and one for transmit. The FXM box was white and contained a base planer with the fiber in and out (chainable) and a backplane with 4 expansion slots for serial cards. I believe each card was 8 or 16 EIA-232 serial ports. It was a step-up from EPORTS in serial expansion for a 3B2. But I'm pretty certain it was only supported on v3 hardware (500 series and up).

    DataKit and first generation ISN was also an interesting option for 3B2s. It was similar to a X.21/X.25-like cloud network for terminals and host machines. The ISN cabinet had 3-4 vertical card bays for serial peripheral cards to connect terminals. Then there were fiber cards to connect host machines. Each terminal initially received a DIAL prompt and you could instance virtual circuits to host ports over the fiber links. It's fatal flaw was it had a single 80186 CPU marshalling all the traffic for up to a hundred physical ports and virtual connections.
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  5. #5


    According to the 3B2 FAQ, the hardware I have installed is:

    2x PORTS 0x0003 Ports card. 4 serial, 1 parallel. (includes HPP)
    1x CTC 0x0005 Cartridge tape controller. 23 MB
    1x EPORTS 0x0102 Extended ports. 8 serial ports
    1x MAU 0xFD00 Math accelerator unit

    Also, when the system shutdown, it turned itself off completely. It did this twice yesterday and I had to hit the ON / STANDBY switch again to turn it on again.
    Today, it did not do it, though I was logged in this time as ROOT.

  6. #6


    Even further to this, the fan on the power supply isn't spinning so my blackouts are probably thermal protection circuits kicking in (or the power supply just crapping out). Will need a new fan...

    I found the other power control connector on the 3B2 and it is some sort of coaxial power connector (the closest I have is an 'N' (5.0mm x 2.5mm) but not exactly the right fit either. Maybe I'll order a few sizes and see if I can't make my own cable.

    Snooping around, I can't find much of anything installed on this thing other than UNIX itself.

  7. #7


    Not all of my replies seem to be posting?

    Found out that the fan is dead so probably a thermal issue causing the 3B2 to shutdown. Will manufacture a power control cable and see if I can't get the XM working too. Anyone have a power control cable that can look at their plug and give me I.D. and O.D. for the coax power plugs?



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