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Need help identifying a 286 motherboard

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mdanh2002

Experienced Member
Joined
Sep 7, 2011
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266
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Singapore
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.
 

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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 :)
 
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.
 
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.
 
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.
 
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.
 
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.
 

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mdanh2002 said:
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?
Click to expand...
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
 
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?
 
Stone said:
Are you using a twisted cable?
Click to expand...

Thanks. Now it boots fine. I was using a short floppy cable taken from another COMPAQ all-in-one Pentium PC. As soon as I changed to a twisted cable the machine boots fine to DOS. The BIOS still complains "equipment configuration error" after POST and ask me to press F1 to continue. Maybe it's due to missing CMOS battery input, or wrong settings on the DIP switches. I've figured that some of them are for memory size (changing those results in a memory size mismatch error), while the other seems to have no effect on the POST. Still a lot to play around :)

For the CMOS battery input, I am planning to use a CR2032 battery. This is the first time I played with a 80286 motherboard. :) My previous experience has always been with 386, Pentium and newer boards.
 
I got the BIOS to remember the settings now. using a 4xAA battery holder with 3 diodes to reduce the voltage to around 5V. The error message regarding system configuration remains.

The board boots ok to DOS but I can't seem get it to detect IDE hard disks. On 3 all-in-one ISA controller cards (with parallel, serial, floppy, and IDE ports) that I've tried, the floppy drive & serial port work (tested with serial mouse in DOS), but not the hard disk drive. Connecting any hard drive and the machine would refuse to boot. No VGA output, no POST beeps, no floppy seeks whatsoever. On another ISA controller card with only IDE & floppy ports, the machine will not hang and boot to DOS 6.22 using the floppy drive fine. However, setting any type of hard disk as the primary fixed disk and the BIOS would complain "error initializing hard drive controller 0". Various DOS utility (IDEDIAG, IDEINFO, WHATIDE) that can identify IDE hard drives independent of the BIOS also can't detect any drive connected.

I have tried on both master and slave IDE channels with no differences. And this issue happens on both CF cards and real 3.5" IDE drives.

Any suggestions? Maybe some settings on the SW1 DIP switches not properly configured?
 
mdanh2002 said:
However, setting any type of hard disk as the primary fixed disk and the BIOS would complain "error initializing hard drive controller 0". Various DOS utility (IDEDIAG, IDEINFO, WHATIDE) that can identify IDE hard drives independent of the BIOS also can't detect any drive connected.
Click to expand...
Does your BIOS allow manually specifying the CHS values for the drive? Or is it limited to selecting from a list of pre-defined drive types? The CHS values must exactly match the drive or most BIOSes will complain like that.
 
SomeGuy said:
Does your BIOS allow manually specifying the CHS values for the drive? Or is it limited to selecting from a list of pre-defined drive types? The CHS values must exactly match the drive or most BIOSes will complain like that.
Click to expand...

No options for entering CHS value. Only accept type 1-47 and 60-90. Usually in my experience, I simply set type 02 (or some small hard disk size) and use ANYDRIVE if the BIOS doesn't support the disk and there should be no errors. The machine also fails to POST if an IDE hard drive is connected on the 3 controller cards that I have. Weird.
 
What happens if the IDE card is in the slot but no drive is attached to it?

What BIOS is on that board? Just a guess but there may be a BIOS conflict with the IDE drives.
 
Stone said:
What happens if the IDE card is in the slot but no drive is attached to it?

What BIOS is on that board? Just a guess but there may be a BIOS conflict with the IDE drives.
Click to expand...

The BIOS is Award BIOS version 3.01C1. Very basic version (something like DOS CHOICE command, e.g. enter 1-4 to select menu) with no fancy user interface stuff.

I tested with 4 controller cards, 3 almost identical with serial/parallel/floppy/IDE ports and 1 with only floppy/IDE controller. I also have another Sound Blaster card with IDE port (true IDE, not a 40-pin IDE-like port proprietary CD drives) I summarized my experiment results below:

1. On all the cards, the floppy controller works fine and boots the system to DOS 6.22 on a 1.44MB floppy disk.

2. On the 3 controller cards with the serial & parallel ports, the system also boots fine from floppy if no IDE hard disk/CD-ROM drive is attached. The serial port also works (tested using a serial mouse). The parallel port is not tested.

3. On the above 3 controller cards, if an IDE hard disk/CD-ROM drive is connected, either on the primary or secondary channel, the system would not POST at all. No VGA output (monitor goes to standby mode), no floppy seeks and of course no POST beeps. NUM LOCK/CAPS LOCK also stop responding.

4. The system also fails to post in the exact same manner if the sound blaster card is connected with an IDE hard disk/CD-drive attached.

5. The 3 controller cards work fine and the sound card also works fine if no IDE device is attached.

I also encountered a similar issue when trying to find the correct VGA card for this board. I have 5 ISA VGA cards. Three of them work fine on another machine but caused this board to beep 3 times when tested. One of them caused the machine to freeze (similar to (3) above, but with blank VGA output). The only one that works is the one I am using now. :)

Now, with the controller card that does not freeze the machine when a hard disk/CD-ROM is connected, the BIOS still complains hard drive error. Various DOS utilities that scans for IDE devices directly without querying the BIOS also fail to find any devices.

Does anyone have any idea what the DIP switches are for? I suspect there are some DIP switches that have to be set for it to work.
 
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