Recently I got this motherboard with Suntac ST62C00x (C008) chipset, AMD 286-16@10 MHz CPU and 1 MB of RAM. The board was very dirty and with leaking battery, but fortunately with very little traces of corrosion. This is how it looks now after some very extensive cleaning and preparation for tinning of couple corroded spots:

It's alive:

I don't know what is the manufacturer or model of the motherboard. The only markings resembling something like brand (PSC ?) and model (220B ?) are on the bottom side of the PCB.

I'm looking for some user's manual or descriptions for the motherboard setting by its jumpers and switches. Fortunately it came to me with correctly set for the 1 MB of RAM in the populated memory banks, but I want to have some clue on how to set this board for different memory configurations. These are the current settings with the 1 MB RAM installed (8 chips x 128 kB):

DSP1 (Sw1-Sw8) - I have no idea what these switches sets (???)
JP10 (SP, 4-pin) - PC speaker connector
JP20(5-pin) - probably power-on led + keyboard lock connectors (?)
JP6 (RESET, 2-pin) - reset button connector
JP7 (TUB, 2-pin) - probably turbo button connector (?)
JP8 (TUBLED, 2-pin) - turbo led connector
EMS (missing, 2-pin) - probably EMS/EXM memory jumper selector (???); I don't know If I can test this with only 1 MB of RAM

There are also 4 missing jumpers next to keyboard controller chip:

JP1 (DISP, 2-pin) - no idea if this is monochrome/color display jumper selector (???)
JP2 (2-pin) - ???
JP3 (2-pin) - ???
JP4 (2-pin) - ???

The board has AMD 286 16 MHz CPU installed, but the CPU crystal oscillator is for 20 MHz, se effectively the processor is underclocked to 10 MHz.

These two boards are very similar (with slight difference in the the jumpers):

Predator99 wrote on 2017-05-28, 11:39:

It looks as it was never installed, battery was removed and slight green corrosion in one ISA slot...but overall conditions is e […]
Show full quote

It looks as it was never installed, battery was removed and slight green corrosion in one ISA slot...but overall conditions is excellent!

The attachment IMG_0059r.jpg is no longer available

The attachment IMG_0061r.jpg is no longer available

Bios message (AWARD) is "HLB-286 SYSTEM"

On the board "MBA-009" is printed, dont know the manufacturer.

Predator99 wrote on 2022-01-22, 19:14:

...also some new Boards:

The attachment IMG_8285r.jpg is no longer available

The closest match ont TRW site is this one (unknown board): https://theretroweb.com/motherboards/s/unknown-suntac-286 Again slightly different jumpers, but the Award BIOS (ver. 3.03HL) is exact binary match.

Unfortunately there are no usable user's manuals uploaded for the most similar boards on TRW site and I have no idea where to look for descriptions about those jumpers/switches settings and RAM banks population. Any help will be appreciated.

UPDATE: Actual info in this post.

UPDATE: Actual info in next post.

Final update: I forgot about missing JP5. I found out that t's a memory wait state 1/0 jumper selector and it duplicates DSP1-Sw1.

This is what I found out by tests for jumpers and switches of this unknown motherboard:

DSP1-Sw1 - memory wait state 1/0 selector switch (duplicated by missing JP5)
DSP1-Sw2 - monochrome/color display selector switch (duplicated by missing JP1 (DISP))
DSP1-Sw3 - memory parity check disable/enable selector switch
DSP1-Sw4 - EMS port address 098H/0E8H selector switch
DSP1-Sw5 - EPROM type 27256/27128(23C128) selector switch
DSP1-Sw6 - populated memory banks configuration** selector switch
DSP1-Sw7 - populated memory banks configuration** selector switch
DSP1-Sw8 - XMS/EMS memory selector switch (duplicated by missing EMS jumper)

** - For memory configurations there are some suitable user's manuals for similar motherboards with Suntac ST62 chipset. On this board here are only two memory banks (0 and 1) duplicated for using of different types memory chips, so it's easy to be figured out how they work.

JP1 (DISP, missing, 2-pin) - monochrome/color display jumper selector - duplicates DSP1-Sw1, useless (one pin is connected to pin 33 of the keyboard controller chip, other - to ground)
JP2 (missing, 2-pin) - both pins bridged and connected by trace to to pin 27 of the keyboard controller chip and to one pin of JP3, unknown function
JP3 (missing, 2-pin) - one pin is connected to pin 23 of the keyboard controller chip, other - to JP2 pins, unknown function
JP4 (missing, 2-pin) - ???, I can't find the connections from/to this one, unknown function
JP5 (missing, 2-pin) - memory wait state 0/1 jumper selector - duplicates DSP1-Sw1, useless
JP6 (RESET, 2-pin) - reset button connector
JP7 (TUB, 2-pin) - turbo button connector
JP8 (TUBLED, 2-pin) - turbo LED connector
EMS (missing, 2-pin) - XMS/EMS memory jumper selector - duplicates DSP1-Sw8, useless
JP10 (SP, 4-pin) - PC speaker connector
JP20 (5-pin) - power-on LED + keyboard lock connectors

I'll not ask questions like which BIOS form Predator99's ST62 BIOSes collection will be the best one to be used with this board, 'cause obviously currently there's zero interest in this Suntac 286 motherboards topic.

Case closed.

Hi,
Does anyone have any information about the M BAY-1000C board, including pinouts, configuration, and manuals?
Thank you very much.

analog_programmer wrote on 2025-04-30, 13:16:

The closest match ont TRW site is this one (unknown board): https://theretroweb.com/motherboards/s/unknown-suntac-286 Again slightly different jumpers, but the Award BIOS (ver. 3.03HL) is exact binary match.

And the original Award BIOS ver. 3.03HL turns out to be the most useless BIOS I've ever seen up to this day. No memory autodetection, no option for HDD user settings, no shadow RAM settings, B/W default "colors" scheme... just pure useless sh*t:

I'm looking for information about the motherboard shown in the photos, including manuals and connections. I don't know where to connect the turbo and the speaker. Does anyone have any ideas? Kind regards.

dennisE wrote on 2025-06-24, 17:29:

I'm looking for information about the motherboard shown in the photos, including manuals and connections. I don't know where to connect the turbo and the speaker. Does anyone have any ideas? Kind regards.

JP10 is pc speaker (named as speaker on the board) 4 pin header)

TUB is Turbo switch
TUB LED is Turbo led.

Thank you so much for your help!
My question is, where are the keyblock pins, the power LED...? JP20, for which one is it?
Best regards.

dennisE wrote on 2025-06-28, 06:49:

My question is, where are the keyblock pins, the power LED...? JP20, for which one is it?

5-pin connector J20 seems like PW-LED + KB-lock.

Jumpers RASS, CASH, CASL - probably for stetting memory timings.

And, Where is the RESET pin?

Hi guys, not sure if I should fork a thread for my Suntac mobo. I have this one:
https://theretroweb.com/motherboards/s/dtk-ptm-1230s

However, I can't get it to POST. When I got it, I found it had two pins (DATA15 and GND) from the 16-bit ISA slot touching, so I separated them off.

Second, I dumped the BIOS ROMs and they were bogus values with no strings readable at all. Unfortunately, the TRW entry for this specific board has no BIOS ROMs uploaded. So I'm wondering if anyone got a dump of this board's BIOS?

I tried to use one of the many other Suntac BIOSes, and I get numbers on the POST card with a beep pattern, but nothing on the screen.

The beep pattern is: One long, two short.. then silence, then two short again. I've attached a recording. The POST card stops on codes 26 25.

I tried toying around with all the jumpers and switches on the board, but it only made the POST process fail earlier and without any beep codes.

Any help with a BIOS dump or things to try would be welcome.

Thanks!

dennisE wrote on 2025-07-01, 16:05:

And, Where is the RESET pin?

For most suntac 286 boards, jumpers are same

wbahnassi wrote on 2025-07-01, 18:25:

I tried to use one of the many other Suntac BIOSes, and I get numbers on the POST card with a beep pattern, but nothing on the screen.

These mobos can be very picky about the VGA card. Try a card that doesn't need ALE to work, many Trident 8900C (but not D) don't have it connected. Try the slots near the edge and the innermost, preferably avoid putting the video card into the middle ones. Not saying it can't work, but I had better results that way. And obviously for initial testing use just the VGA card, nothing else in the system. Are you sure your RAM is good?

BTW what's wrong with the original BIOS? Can you upload the images somewhere?

Deunan wrote on 2025-07-01, 23:35:

These mobos can be very picky about the VGA card. Try a card that doesn't need ALE to work, many Trident 8900C (but not D) don't have it connected. Try the slots near the edge and the innermost, preferably avoid putting the video card into the middle ones. Not saying it can't work, but I had better results that way. And obviously for initial testing use just the VGA card, nothing else in the system. Are you sure your RAM is good?

For VGA, I'm using an ATI VGA Charger.. It's a 16-bit card, but looking at its ALE pin on the connector, I can see it's not connected.
I tested continuity across the ISA slots, and all pins connect properly. But I did also try the VGA in several slots, didn't make a difference.
I also probed the ISA pins and they all seem good, except for Address 20 pin (on the 16-bit extension part).. that one was not showing any activity.. However, I was also able to trace its connectivity to one of the Suntac chipsets, so I don't think there is a disconnect there.

I can't say I'm sure about the RAM. Can these chips be tested in the XGecu programmer? I did take them off and reseat them anyways.

Deunan wrote on 2025-07-01, 23:35:

BTW what's wrong with the original BIOS? Can you upload the images somewhere?

I still have the original BIOS chips, and I dumped them. The dump is attached. When I looked at the dump, I couldn't find any strings that are typically found in BIOSes (e.g. dates, model, version, ...etc). With this original BIOS, the mobo goes into an endless loop of restarts. I can see that on the POST card and notice the infinite loop of codes occurring, so I decided to try another BIOS. The one I'm using now is an AWARD BIOS. I took it from here:
https://theretroweb.com/motherboards/s/panatek-pk-009#bios (the second entry with version 3.03HL)

I tried many other Suntac BIOSes, but the Award ones seem to get the farthest during POST. There are Phoenix BIOSes too, but they hang very quickly on POST, whereas Award seems to advance in progress for about 2-3 seconds before finally resting on the 25 26 code.

dennisE wrote on 2025-07-01, 16:05:

And, Where is the RESET pin?

Try JP6.

wbahnassi wrote on 2025-07-01, 18:25:

The beep pattern is: One long, two short..

I've heard this pattern with my Award 3.03HL. It's for videocard problem.

This Award 3.03HL BIOS is a cr*p - there's no option for user defined HDD.

wbahnassi wrote on 2025-07-02, 02:06:

I still have the original BIOS chips, and I dumped them. The dump is attached. When I looked at the dump, I couldn't find any strings that are typically found in BIOSes (e.g. dates, model, version, ...etc). With this original BIOS, the mobo goes into an endless loop of restarts. I can see that on the POST card and notice the infinite loop of codes occurring, so I decided to try another BIOS.

Well it looks fine to me: "PTM - U28 & PTM - U51 DATATECH ENTERPRISES CO., LTD. 286 LABEL BIOS (C) COPYRIGHT 1985,1986 ALL RIGHTS RESERVED."
I combined the two halves and the 8-bit checksum is correct (zero), so here's the resulting file attached. I think the BIOS, as such, is only the second 32k - aka the SETUP part. The first 32k is a separate piece of code that is the UTIL/DIAG part with HDD low level format and some diagnostic tools. Very useful actually, it's just that its split and the SETUP part is usually just one page with no extra features to set. These mobos are setup with jumpers anyways.

A20 behaviour might be correct, as it should be masked/gated before programs such as HMEM can re-enable it. As for the VGA, do you have any other cards to test? Maybe this mobo just doesn't like this one for some reason.

Just looked into wbahnassi's BIOS dump files. This is not Award BIOS ver. 3.03 HL, but Award BIOS ver. 3.25 S dated 03/01/89. Maybe it's better than ver. 3.03 HL. As Deunan wrote dumps are fine, checksum is OK.

The problem is with videocard and the error sound pattern (1 long + 2 short beeps) confirms this.

Sounds good. Let me describe what I have experimented with so far:

Using Award 3.03 BIOS:

• ATI VGA Charger card in different 16-bit slots - No progress
• ATI VGA Charger card in different 8-bit slots - No progress (this card usually works in 8-bit slots as well)
• Trident TVGA8900CL in different 16-bit slots - No progress
• EGA Ultra card (8-bit) - No progress
• MDA card (8-bit) - No progress

All the above is still resulting in the same beep pattern. I also tried fiddling with the jumpers and switches with all possible combos.. no avail.

I then restored the original Award 3.25 BIOS chips and gave it another run. This one makes just one short beep directly on power-on. The POST card shows codes 00, AA and FF only. Nothing more elaborate. Depending on switches, there are three results:

• One short beep on power-on, POST codes start from 00 to AA to FF and then stays there forever.
• One short beep on power-on, POST codes start from 00 to AA to FF and then resets automatically to 00 and the pattern repeats infinitely.
• A mix of angry short and long beeps. This happens when I misconfigure the RAM switches to something beyond the 1MB chips I have on-board.

I used also both ATI and Trident VGA cards with this BIOS, and both couldn't make a progress. I'm starting to feel there is something else going on other than just the BIOS and jumpers. Though my probings indicated that all is good so far. Any suggestions on things to look for? As I said before, ISA signals seem to be all good here.

Deunan wrote on 2025-07-02, 08:43:

Well it looks fine to me: "PTM - U28 & PTM - U51 DATATECH ENTERPRISES CO., LTD. 286 LABEL BIOS (C) COPYRIGHT 1985,1986 ALL RIGHTS RESERVED."

What tool did you use to extract that string? Looking straight at the files in a basic binary viewer didn't yield anything human-discernible to me.