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 […]
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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.

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

There are also 4 missing jumpers next to keyboard controller chip: […]
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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) - ???

Some update on these missing jumpers: Both pads of JP1 (DISP) are internally connected to ground, so it's useless. Both pads of JP2 are connected by a trace (on the bottom side of the board) to one of the pads of JP3, so JP2 is also useless without cutting the trace between it's two pads.

JP1 (DISP, 2-pin) - internally shorted to ground
JP2 (2-pin) - both pins bridged and connected by trace to one pin of JP3
JP3 (2-pin) - ???
JP4 (2-pin) - ???

Another quick update: JP1 (DISP, 2-pin) is duplicated by DSP1-Sw1 (when Sw1 is on it also shorts JP1 to ground) and EMS is duplicated by DSP1-Sw8.

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

I'm looking for some user's manual or descriptions for the motherboard setting by its jumpers and switches. Fortunately it came […]
Show full quote

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/XMS memory jumper selector (???); I don't know If I can test this with only 1 MB of RAM

DSP1-Sw2 - monochrome/color display selector switch (duplicated by JP1 (DISP))
DSP1-Sw8 - EMS/XMS memory selector switch (duplicated by EMS jumper)
DSP1 (Sw1, Sw3-Sw7) - ???

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) - EMS/XMS memory jumper selector - duplicates DSP1-Sw8, so it's useless

analog_programmer wrote on Yesterday, 10:49:

Some update on these missing jumpers: Both pads of JP1 (DISP) are internally connected to ground, so it's useless. Both pads of […]
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Some update on these missing jumpers: Both pads of JP1 (DISP) are internally connected to ground, so it's useless. Both pads of JP2 are connected by a trace (on the bottom side of the board) to one of the pads of JP3, so JP2 is also useless without cutting the trace between it's two pads.

JP1 (DISP, 2-pin) - internally shorted to ground
JP2 (2-pin) - both pins bridged and connected by trace to one pin of JP3
JP3 (2-pin) - ???
JP4 (2-pin) - ???

JP1 (DISP, 2-pin) - monochrome/color display jumper selector - duplicates DSP1-Sw1, useless
JP2 (2-pin) - both pins bridged and connected by trace to one pin of JP3
JP3 (2-pin) - ???
JP4 (2-pin) - ???

P.S. Apologies for the new post, but my right to edit my previous posts has been taken away some time ago.

analog_programmer wrote on Yesterday, 11:43:

Another quick update: JP1 (DISP, 2-pin) is duplicated by DSP1-Sw1 (when Sw1 is on it also shorts JP1 to ground) and EMS is dupli […]
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Another quick update: JP1 (DISP, 2-pin) is duplicated by DSP1-Sw1 (when Sw1 is on it also shorts JP1 to ground) and EMS is duplicated by DSP1-Sw8.

DSP1-Sw2 - monochrome/color display selector switch (duplicated by JP1 (DISP))
DSP1-Sw8 - EMS/XMS memory selector switch (duplicated by EMS jumper)
DSP1 (Sw1, Sw3-Sw7) - ???

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) - EMS/XMS memory jumper selector - duplicates DSP1-Sw8, so it's useless

JP1 (DISP, 2-pin) - monochrome/color display jumper selector - duplicates DSP1-Sw1, useless
JP2 (2-pin) - both pins bridged and connected by trace to one pin of JP3
JP3 (2-pin) - ???
JP4 (2-pin) - ???

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.

P.S. Apologies for the new post, but my right to edit my previous posts has been taken away some time ago.