Upload your dump here. Im pretty sure it will come back fine, but one never knows.
https://theretroweb.com/motherboards/s/acer-1 … 9119-acermate-1 suggests it came with two types of bioses, AMI and Acers own? will have too look into the bios code to see what those Post codes (02, E4) mean.

>Reseated chips on motherboard ja cleaned contacts.

have you tried different ram chip? different bank? ISA VGA card instead of Acer module?

edit: looks like Acer had two different mobos going into 1120SX. The kind you have, 8 simm sockets, same as on theretroweb picture, and the 6 simm sockets one that is on retroweb jumper document and here https://aukro.cz/acer-1120sx-80mb-5-25-retro- … 3757-7089964233 and Acer 1120SX
The 6 socket one is probably the older design with soldered in 2MB of ram and legit decent AVGA graphic card.

rasz_pl wrote on 2026-07-27, 00:00:

Upload your dump here. Im pretty sure it will come back fine, but one never knows. https://theretroweb.com/motherboards/s/acer-1 […]
Show full quote

Upload your dump here. Im pretty sure it will come back fine, but one never knows.
https://theretroweb.com/motherboards/s/acer-1 … 9119-acermate-1 suggests it came with two types of bioses, AMI and Acers own? will have too look into the bios code to see what those Post codes (02, E4) mean.

>Reseated chips on motherboard ja cleaned contacts.

have you tried different ram chip? different bank? ISA VGA card instead of Acer module?

edit: looks like Acer had two different mobos going into 1120SX. The kind you have, 8 simm sockets, same as on theretroweb picture, and the 6 simm sockets one that is on retroweb jumper document and here https://aukro.cz/acer-1120sx-80mb-5-25-retro- … 3757-7089964233 and Acer 1120SX
The 6 socket one is probably the older design with soldered in 2MB of ram and legit decent AVGA graphic card.

Dump on attachment. Tested it on ChatGPT it says that dump is not corrupted but also AI can be wrong.

All memory banks filled when got that computer. Tested two memory sticks but same error. Without memories different code. If bank 0 empty different code.

Also tested with ISA VGA card, but same code. Sometimes ISA Post card stuck 242 but when moving and pressing motherboard it goes to E42.

Yep, that motherboard is different than retroweb model.

BIOS is fine.

1ACER0043 8038633 1.00 08/29/89
2043 386SX20 1.00 05/16/90
380386SX ACER BIOS V1.00

And what a weird and quirky BIOS it is
- MFM formatting helper tool uses Dos terminated strings. Usually BIOSes stick to Pascal strings or 0 termination.
- simultaneously outputs POST codes to a POST card and all Printer ports. Apparently this doesnt trigger Printer to print 😮
- BIOS teletype interrupt actually DOES support serial terminals 😮 none of the less famous bioses I disassembled do that

Adding it to my bios disassembly zoo https://github.com/raszpl/ACER_BIOS <- quickly disassembled bios, missing headers, nice names and annotations.

Now I had another look at your first post and there is something wrong with your POST card, those cards normally dont have the ability to display 3 characters, its 2 or 4. "242" and "E42" are invalid readings. Is your POST card confirmed working? have you tested it in another working computer? Try it in another slot, take a loupe and look carefully for any soldering bridges on the card if it keeps showing garbage readings. There were cases of badly assembled cards, Jo22 had one Re: GA-586S motherboard woes

FWIW the BIOS dump contains (at the indicated HEX offsets):

E359 "Warning! ACER INC copyright violated."
3603 "0043 386SX20 1.0005/16/90"
361E "80386SX ACER BIOS V1.00 "
3637 "ACR68"
E149 "Copyright (C) Acer Incorporated 1989"
FFF5 "07/20/89"

So it looks to be V1.00 of an Acer BIOS generated or updated on: July 20, 1989
and possibly released: May 16, 1990

I don't see any obvious error messages for BIOS checksum - but who knows if would even try to start if it things the BIOS is in error - This would be tested very early on entry - I'd have to do a bit of disassembly to figure out what it tests/expects...

(Looks like @rasz_pl has something suitable to launch it on and confirmed that it starts OK - which would have passed any internal self-test)

rasz_pl wrote on 2026-07-27, 11:20:

... - simultaneously outputs POST codes to a POST card and all Printer ports. Apparently this doesnt trigger Printer to print :o […]
Show full quote

...
- simultaneously outputs POST codes to a POST card and all Printer ports. Apparently this doesnt trigger Printer to print 😮
...
Now I had another look at your first post and there is something wrong with your POST card ...

So... should be able to read post code with a multimeter testing the parallel port output pins?

(Fwiw - as long as LPT doesn't hit strobe "noise" on the port shouldn't affect an actual printer - I like this idea and wish more BIOS did this!)

DaveDDS wrote on 2026-07-27, 11:33:

So... should be able to read post code with a multimeter testing the parallel port output pins?

last reading yes, wow thats so smart and obvious at the same time, nice one! Im always overcomplicating things, was gonna propose $5 logic analyser (https://sigrok.org/wiki/Lcsoft_Mini_Board) or buying another POST card

This is the Post code output routine, called 36 times + 9 more times directly in very early bios:
https://github.com/raszpl/ACER_BIOS/blob/bc55 … 0.BIN.lst#L4839

Fincomputer if you have a multimeter boot the computer and check voltage levels on D0-7 pins of printer port
pinout https://www.bristolwatch.com/pport/index.htm

DaveDDS wrote on 2026-07-27, 11:27:

FWIW the BIOS dump contains (at the indicated HEX offsets): […]
Show full quote

FWIW the BIOS dump contains (at the indicated HEX offsets):

E359 "Warning! ACER INC copyright violated."
3603 "0043 386SX20 1.0005/16/90"
361E "80386SX ACER BIOS V1.00 "
3637 "ACR68"
E149 "Copyright (C) Acer Incorporated 1989"
FFF5 "07/20/89"

So it looks to be V1.00 of an Acer BIOS generated or updated on: July 20, 1989
and possibly released: May 16, 1990

I don't see any obvious error messages for BIOS checksum - but who knows if would even try to start if it things the BIOS is in error - This would be tested very early on entry - I'd have to do a bit of disassembly to figure out what it tests/expects...

(Looks like @rasz_pl has something suitable to launch it on and confirmed that it starts OK - which would have passed any internal self-test)

That unit manufactured 1991 (from stamp in case). BIOS looks same type as My other AcerPower 486SX.

Checking if ISA Post card has something wrong. Purchased it from eBay China many years ago.

Tested clean motherboard with alcohol. And heated biggest chips with hot air station.

Also tested with AT psu which has -5v voltage. But using mainly ATX psu converted to AT. (Accidentially psu +3.3v wire touched one oscillator case (could that break something?) psu shutdown after it.

But still not working.

rasz_pl wrote on 2026-07-27, 12:05:

... if you have a multimeter boot the computer and check voltage levels on D0-7 pins of printer port ...

I was about to say that if you don't have a multimeter (there are people playing with hardware stuff that don't?) - it would be trivial to make a DB-25 plug with LEDs to see the code.

Years ago, I made such a thing (with passthrough) so I could place it in-line - with two LEDs on all "active" signals (one to +5 and one to Gnd so I could see if driven high or low), which I used to "debug" all kinds of parallel interface devices, both off-the-shelf ones and things I was home-brewing at the time.

Came in very handy in lots of cases.

DaveDDS wrote on 2026-07-27, 13:16:

Years ago, I made such a thing (with passthrough) so I could place it in-line - with two LEDs on all "active" signals (one to +5 and one to Gnd so I could see if driven high or low), which I used to "debug" all kinds of parallel interface devices, both off-the-shelf ones and things I was home-brewing at the time.

Although to be fair - if you want to make something to make this kind of thing easier...

I'm sure I still have it, but I do so little of this kind of interfacing these days that I've not taken the time to dig the monitor described above out when I rarely want to use it.

Instead, I use these, just because they make the signals easy to probe, and have the ability to disconnect/reroute if I want (sometimes handy when you are building something to "talk" to a DB-25 interface) - but mostly because I use them often enough for other things that I know where they are 😀

Things were certainly more interesting before AMI and Award became so ubiquitous in the mid 90's. I was just working on a DTK with an in-BIOS calculator app.

Many Bothans wrote on 2026-07-27, 15:14:

Things were certainly more interesting before AMI and Award became so ubiquitous in the mid 90's. I was just working on a DTK with an in-BIOS calculator app.

https://github.com/raszpl/DTK_BIOS 😀

EDiT: Acer bios is full of surprises. It might have Serial console BIOS access 😮 at least something like this sits here:

https://github.com/raszpl/ACER_BIOS/blob/3ca1 … .BIN.lst#L17501

rasz_pl wrote on 2026-07-27, 15:37:

Many Bothans wrote on 2026-07-27, 15:14:

Things were certainly more interesting before AMI and Award became so ubiquitous in the mid 90's. I was just working on a DTK with an in-BIOS calculator app.

https://github.com/raszpl/DTK_BIOS 😀

Fantastic! I just submitted DTK 386 BIOS v4.23 to TRW this week. Keep up the excellent work, I know it helped me better understand my Zenith's MFM-300!