Have you looked at th99 or its modern equivalent?
Chances are you can identify it visually.

I like this kind of 386 board. Full length, forest green, and a true 386 chipset with discrete cache controller…and the option for 128kb double banked cache. I used to see a lot of boards like this, it seems the TACT boards were all more or less the same regardless of manufacturer。I normally don’t see them with quadtel bios though.

I had a look on TH99. I couldn't find it. I remember trying to find a different TACT board several years ago and couldn't find that one either.
A lot of them seem to have 64kb soldered SRAM, which kind of implies they might be an OEM product.
In any case, the board has very few jumpers so they should be easy to figure out.

Anonymous Coward wrote on 2022-04-10, 15:26:

I had a look on TH99. I couldn't find it. I remember trying to find a different TACT board several years ago and couldn't find that one either.
A lot of them seem to have 64kb soldered SRAM, which kind of implies they might be an OEM product.
In any case, the board has very few jumpers so they should be easy to figure out.

yes, it has eight 8k x 8 chips. If it means it has 64kb cache then it might be the case. Upon the close inspection I found just two jumpers JP5 and 6. I haven’t found previous or subsequent jumper numbers yet. I might try to find a pga 386 CPU and see if it works. I sort of like the design.

Try looking on https://www.ultimateretro.net/en/. It used sites like TH99 at the start, but has massively added to it, fixed lots of errors in the database, and is searchable. As well as being added to on a daily basis, with user input welcomed.

debs3759 wrote on 2022-04-10, 20:27:

Try looking on https://www.ultimateretro.net/en/. It used sites like TH99 at the start, but has massively added to it, fixed lots of errors in the database, and is searchable. As well as being added to on a daily basis, with user input welcomed.

eeew... They changed the Search with Images to include photos of the motherboards... 😠 This gives an incredibly messy view and its now much harder to find something because the visual style constantly changes.

debs3759 wrote on 2022-04-10, 20:27:

Try looking on https://www.ultimateretro.net/en/. It used sites like TH99 at the start, but has massively added to it, fixed lots of errors in the database, and is searchable. As well as being added to on a daily basis, with user input welcomed.

I tried to search for the mb there, but haven’t find it yet. Does anybody know the manufacturer of the TACT chipset? Because I didn’t find it in the list of chipsets. So I searched the database according to numbers of 8 and 16 bits ISA slots.

TACT is from Texas Instruments.

If I had to guess the jumper between the cache sockets and Austek controller is probably for enabling the 2nd set of 64kb cache.
JP6 is less clear, but maybe a mono/colour switch, or something related to the keyboard controller.

Thank you, with The search filter set to TI, TACT chipset I found some boards looking like mine with a different layout though.
However on my board I can’t figure out how the 386 and 387 should be inserted in the sockets because there’s no sign for pin one on it. I plan to buy a 386. So far I found just intel 386 DX 25MHz and AMD DX 40 MHz. Are there a chances they would work at 33MHz?

figuring out the pins is likely as easy as looking up the pinout and using a multimeter to measure out some groundpins. though be aware of the view of the pinout. (top bottom)

The 25 might have a chance of working, it'll be overclocked an run hotter, though the 40 will work for sure.

Actually the chipset gives a clue to finding Pin one. Cannot see in the picture for the sockets but the one, you may be able to see on the board by tilting and rotating it around in bright light for the other.

Both processors sockets appear to have arrows pointing to pin 1. (bottom left hand corner).

I saw that too and the 387/87DLC/3167 socket has the key pin on that same side. One quirk: as I looked thru 386 BIOS collection at all the boards not one had the CPU and MathCo pointed exactly same direction.
It is possible but if mine would do some double checking before putting a 386 cpu in the socket near JP6

The placement of the sockets seems pretty random. While the FPU and CPU don't usually point in the same direction, sometimes they do. At least, I am pretty sure one of my boards is like that.

Finally I sourced a 386 cpu for the board. After a proper inspection and with the knowledge I got from you I identified the correct position for CPU. The problem is that when I attempt to power the board on the psu won’t start at all only a silent whistling can be heard from it. What could possibly be the problem? Can someone tell me, what is the jumper J3 for?

just a guess.

psu no start, silent whistling... shorted voltage rail. possible causes... dead tantrum cap, P8P9 put the wrong way round, cpu not correctly oriented, ...

Well the PSU is connected correctly I’d guess - P8 at PS1 and P9 at PS2. To troubleshoot the caps I have to find someone who can do it. To insert the PSU I followed the markings on the board and it should be seated correctly. The PSU won’t start even if the CPU is unplugged. So there’s a short somewhere on the board? Could it be related to the jumper J3 which I don’t know the purpose?
After a proper inspection I found several burned caps close to ISA slots. I hope the board did not get damaged to much. I wonder if it would work after I have them replaced. If the board is worth saving.

There are 54 10uF caps (some of them are rated as 10V some 16V) Do you think I should replace all of them when they are so flammable?

The PSU looks like it is connected right (always remember, black wires should be next to each other, and it should require pressure to insert when they are oriented right). I would change all the caps of the same type as those that are burned.