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Thread: Need help identifying a 286 motherboard

  1. #1

    Default Need help identifying a 286 motherboard

    Hi,

    Can anyone help me identify my 286 motherboard (attached photos) and probably find the manual for it? I bought it from eBay in early 2016 but only decided to try it now, after almost 2 years! It was sold in working conditions, with 2MB RAM onboard (the board apparently caters for a maximum of 4MB, so around 50% of the memory sockets are empty). It has a 12.5MHz 80286 CPU and a 80287 co-processor. The few identifications I can find that could even be remotely useful are the following:

    (1) 910/900(12) PB87011-3A. MADE IN TAIWAN (R.O.C) on the front
    (2) CADAC CMVO-1 2089 at the back

    The board has no output pins for the PC speaker, just a cheap soldered piezzo buzzer. There is no CMOS battery socket on board, and I cannot identify any Dallas RTC. 3 other ICs on the board are labelled as "U41-2" (near the BIOS), "U72-2' and "U68-2", obscuring the original part number. There are a few other connection headers, which I am hoping could be the CMOS battery input or the PC speaker output.

    The board also seems to have a few patches such as jumpered wires or capacitors hand-soldered across pins, which look rather unprofessional.

    Any advice is appreciated. I am trying to find the manual before I attempt to power it on.

    Thanks.
    Attached Images Attached Images

  2. #2
    Join Date
    Jul 2010
    Location
    Silicon Forest, Oregon, USA
    Posts
    637

    Default

    Nothing fancy, looks like a Chips and Technologies NEAT chipset based motherboard.

    It might be an Acer 900/910 motherboard. Here is a YouTube video of a person trying to get a computer with such motherboard to work.

    It uses the 82C206 Integrated Peripherals Controller that integrates the RTC, so you won't see a separate Dallas or any other RTC IC. It should be a 4-pin connector for connecting an external battery pack. (By the way it always puzzled me why later 386-486 chipsets didn't integrate an RTC... such a simple device compared to everything else. May be it has to do with the low power requirements of RTC, and inability to combine high speed and low power logic on the same IC)

    There is nothing unprofessional about the rework on the back side of the board, it is rather nicely wired. Some IBM motherboards had reworks as well.

    I say, just connect a display card, a power supply, power it up, and see how it works

  3. #3
    Join Date
    Oct 2014
    Location
    near frankfurt/m, germany
    Posts
    562

    Default

    Yes, it's the NEAT chipset. At it's time this was a great chipset. You will see, the chipset settings in the BIOS setup of a NEAT board are a science of itself. But you can win some performance with the right settings...

    As I remember there were also some DOS tools to setup the NEAT chipset, they usually had some sets of very effective presets which could be easily used.

  4. #4

    Default

    The best feature of the NEAT chipset is its ability to run QRAM which is a memory manager that is in some ways similar to QEMM. QEMM is only for 386+ while QRAM works on a 286 with a NEAT chipset.
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  5. #5

    Default

    Thanks all for the detailed info. I will try the board tomorrow.

    Any ideas where the CMOS battery input header could be on this board? Also is there a PC speaker output, or do I have to desolder the buzzer and make my own connection header?

    Thanks.

  6. #6

    Default

    Could do with a better picture but generally the CMOS battery header is a 4pin connector with one missing, usually located near the keyboard connector and/or around the back of the ISA slots. The speaker connector is a 4-pin connector. On this board it may be located in front of the two bios chips. It's very hard to see in the image. It looks like the keylock+LED connector has been replaced with a locking-style white connector. There could be a jumper to configure the speaker. Need a better image.
    Looking for: OMTI SMS Scientific Micro Systems 8610 or 8627 ESDI ISA drive controller, May also be branded Core HC, Please PM me if you want to part with one.

  7. #7

    Default

    Attached are the close-up photos of the connector headers on the board.

    Apparently there are no visible jumpers on this board, except for the 8 DIP switches near the BIOS chips.

    From your description, connector J4 (near the PS2 port) is most likely for the CMOS battery, since it has 4 pins with one missing. Any ideas what is the pinout for it?

    The PC speaker *might* be connector J1, though I am still skeptical. I will use an oscilloscope and probe J1 to see if there's any audio waveform before connecting it to an 8-ohm speaker.
    Attached Images Attached Images

  8. #8

    Default

    Quote Originally Posted by mdanh2002 View Post
    From your description, connector J4 (near the PS2 port) is most likely for the CMOS battery, since it has 4 pins with one missing. Any ideas what is the pinout for it?
    That's not a PS/2 port; it's a standard (XT/AT) keyboard connector.

    Code:
    Backup Battery Connector
    
        Pin    Signal
    -----------------------------
         1  -  Batt+
         2  -  [KEY]
         3  -  GND
         4  -  GND
    
    
    Speaker Connector
    
    
        Pin    Signal
    -----------------------------
         1  -  -Speaker
         2  -  [KEY]
         3  -  GND
         4  -  +Speaker +5v
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

  9. #9

    Default

    Thanks for the correction. I called it PS2 simply because I can connect my PS2 keyboard to it via an adapter.

    I tested the board today and it seems to post fine, detecting 2048KB of RAM. However, it does not seem to boot from floppy disk (saying DISK BOOT FAILURE), even after I set Floppy Drive A to 1.44MB. I can hear the floppy seek sounds at startup and the floppy LED lights up for a while. However, the BIOS does not seem to read from the floppy disk at all and simply reports the boot error. Also, the BIOS still complains "equipment configuration error" even after i have adjusted the BIOS setup settings.

    The floppy drive works fine on another computer.

    Any ideas what's wrong?

  10. #10

    Default

    Are you using a twisted cable?
    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen
    ☞ Time flies like an arrow; fruit flies like a banana.

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