I was able to guess some dip switches meaning. Now FPU works fine and did not crash the whole system. But some options are still unclear. No luck with the SW 2, I'm unable to boot PC without populated DIP memory with any possible combination.

Prepared a board layout draft, I'd like to add this motherboard to ultimateretro database later.

SW1:
1. Weitek FPU (enable/disable)
2. 80387 FPU (enable/disable)
3. unknown
4. unknown
5. COM1 (enable/disable)
6. COM2 (enable/disable)
7. LPT (enable/disable)
8. LPT IRQ

Great ! Can you dump the BIOS ?
There are only two Wearnes vintage boards at Ultimate Retro: https://www.ultimateretro.net/en/motherboards … ufacturerId=519
and the semi-old Wearnes PC support only lists newer Athlon, Pentium 2, etc computers: http://web.archive.org/web/20001204003300/htt … ort/support.htm

Horun wrote on 2022-07-02, 15:53:

Great ! Can you dump the BIOS ?

It is already dumped, see my first post )

🤣 yeah somehow I missed that ;p
It does load in PCem so is a good bios dump, thanks !!
In a Singapore biz list from late 80's and early 90's it lists Wearnes having a big stake in ALR (until bought by Gateway) so it could be an ALR board but does not match any at Ultimate Retro 🙁

It *could* be an ALR board, but I think it's unlikely. This board is quite clunky for 1990. It looks more like something designed for 1987. ALR was usually cutting edge.

Anonymous Coward wrote on 2022-07-03, 01:29:

It *could* be an ALR board, but I think it's unlikely. This board is quite clunky for 1990. It looks more like something designed for 1987. ALR was usually cutting edge.

Yeah, it looks like it doesn't use an integrated chipset in the normal sense?
I was wondering whether those DIP switches are read by the BIOS and change its behavior (in which case it might be possible to peek at the BIOS and determine what they do), or if they directly affect the circuitry on the board.

Agree ! Yeah I was just making a guess. The main VLSI are for Peripheral only and think all the white labeled U** are PALS making it a very odd mix of things. Sort of like the DTK PEM-3301 (which I have one)
Re: What retro activity did you get up to today?
A very dinosaur designed board for 386DX ! Most likely those dips are read by the PAL's and change the addressing of ports and memory directly thru the logic and the BIOS just reads it... just a guess 😀

I suppose that you are right. Did the simple continuity check and found that U84 responsible for the SW2.
Have tried to boot without populated DIP, four 1MB SIMM was installed, no boot with all possible combination of SW2.

Did not finish all the combination with installed DIP modules but found the following patterns:
Let’s mark Off position as 0, On position as 1 and X as any value, then
X X X X 0 0 X X boot as 640K
1 1 1 0 0 1 0 0 boot as 1664K
1 1 1 0 0 1 1 0 boot as 1664K
1 1 1 0 0 1 1 1 boot as 1664K
1 1 0 1 0 1 0 0 boot as 2688K
1 1 0 1 0 1 1 0 boot as 2688K
1 1 0 1 0 1 1 0 boot as 2688K
X X X X 1 X X X did not boot
All other combination boot as 3712K
It looks like SW2 can configure only onboard memory.

So, no more ideas how to configure additional SIMM modules ☹

Hmm reminds me of a old DFI motherboard where one 3 pin jumper changed RAM from DIP to SIMMs and the switches set total memory and if UMB or EMS.
Not the same but the 286 DFI Concorde-L and V versions did similar memory settings. [see: https://www.ultimateretro.net/en/motherboards/1683 ]
So the board sets the 384k UMB outside (1664k+384k=2Mb, 2688K+384k=3Mb, 3712k+384K=4MB) similar to those DFI. Interesting !
It looks like the board has 2 banks for DIPS and 2 banks for SIMMs. I wonder what happens if you remove 18dips (the two far right rows in picture) and add just 2 x 1MB SIMMS and then see what the switches do.
Yeah a lot of work but did similar on a board just to get the SIMM sockets working (did not care about the DIPs so much as SIMMS are truly more reliable/easier to change out)
Just some thoughts rambling around ;p

Is it possible that 4MB is simply the most that board can take?
BTW, that ISA-like connector underneath the DIP RAM is usually associated with proprietary RAM cards, so that could be another variable...

You could look at the pinout here: http://www.interfacebus.com/Memory_Modules_30 … IMM_PinOut.html
and see if the Address 10 pin goes anywhere on your board. It would need to for it to take 4MB SIMMs.

Excellent points Jake ! Being a 386DX would assume up to 16MB ram minimum but based on its somewhat "antiquated" design maybe it maxes onboard at 4MB like you say.
And those DIP sockets look like they can use either 256kx1 or 1Mx1. Maybe with 256kx1's you can add SIMMS to Max 4MB and use a add-on card for more.
Will load the BIOS in PCem again and see if I can get more than 4MB to work (is not a guarantee but maybe the BIOS will puke/error on 8MB ??? just a thought)..
Yeah BIOS appears to see 8MB but that means nothing really. Very basic BIOS, worse than most 286 BIOS clones imho...

Horun wrote on 2022-07-05, 01:44:

I wonder what happens if you remove 18dips (the two far right rows in picture) and add just 2 x 1MB SIMMS and then see what the switches do.
Yeah a lot of work but did similar on a board just to get the SIMM sockets working (did not care about the DIPs so much as SIMMS are truly more reliable/easier to change out)
Just some thoughts rambling around ;p

So, no luck again 🙁
It didn't boot with this configuration. Have check all possible combination with jumpers 5, 7, 10, 11 and SW1 switches 3,4. It stooped at 10 0C POST followed with 3 beeps.
Tried to run THE LAST BYTE memory manager 2.52 CHIPSET tool, it didn't recognize any memory controllers on board.

Next will try to trace the Address pins from SIMM sockets.

P.S. Noticed that during the boot it shows the additional 384K of memory, see the screen attached, don't remember is it was there before or not.

Been keeping an eye on this thread. Have you tried sticking 4 1MB simms in it as well as the dip?

I would doubt it can take 4MB simms as it was made in 1990 and, it has that memory expansion connector, but i may be wrong.

I forgot to ask what type 30 pin SIMMS ? Are they 9 chip type ? What exact chips are on your SIMMS ? They need to be 80nS or faster and:
They may need be same as what the DIP chip layout is with 9 - 256k x1 or 9 - 1Mb x 1 chips on each and not the 3 chip variant 30Pin SIMMs.
just a thought...since it has no dedicated Memory Controller and uses mostly TTL for the memory addressing it could be very specific on what ram type it can use.....

Horun wrote on 2022-07-06, 01:09:

I forgot to ask what type 30 pin SIMMS ? Are they 9 chip type ? What exact chips are on your SIMMS ?

I did not pay attention to this fact. All my modules has 3 or 8 chip type. Will order some for test and come back with the results. It will be SIMM (9-1Mx1) with 9xTC511000AP-80 and 9xHYB511000BJ-60, 8 SIMM in total, hope they will work.

Short update.
Just finish quick tests with the new SIMM modules (4 Toshiba modules + 4 Siemens +2 Mitsubishi), no result 🙁 Memory test stopped at 3712 as before
Will try to boot with half onboard memory and 2 simms and trace address lines from simm tomorrow.
I suppose this modules should fit this board now, isn't it?

Got that incorrect.

386dx requires 32bits data path this means you have to fill 4 slots at a time using matched set of four modules. You said final two. That's the problem. Put only 4 modules in. I think board might takes either dip memory chips or set of four SIMMs.

Keep trying the switch combinations, there is a jumper, what it does?

Cheers,

I agree ! Without knowing how the memory banks are layed out, using 2 SIMMS will not work and neither will the idea of using two DIP rows and two SIMMs will not work, sorry I suggested trying it earlier.
Remove the DIPS and try just 4 matching SIMMS. Can you take a picture with the DIPS removed ? Knowing the U# may help figure out how the memory banks are laid out... just a thought.
added: I would try the Toshiba Simms first, have had good luck with similar..