That is a DX4-100. The 25253 matches my A80486DX4-100NV8T. Don't worry about JP15, none of the TRW pictures have it either..just set it to 80486DX4-100
Who scratched the the writing off the cpu in your picture ?

Horun wrote on 2024-10-02, 22:13:

That is a DX4-100. The 25253 matches my A80486DX4-100NV8T. Don't worry about JP15, none of the TRW pictures have it either..just set it to 80486DX4-100
Who scratched the the writing off the cpu in your picture ?

Hi, thanks for the respond! When i bought this MBO, CPU, RAM, and cleaned the thermal paste out of CPU, that is how it looked. I will try to find jumer settings, but it also have only AMDX/DX2 on retro web, and 80486DX4, but there is no AMDX4 settings. So i need to set things to 80486DX4?

I tried but i didn't make it work. I tried CPU on other mbo, and it is 100MHz, working fine. But there is no sound from speaker without RAM??? I need to find where could lie the problem.....

Here are some pictures from Aukro.cz that show same board running an AMD DX4-100, shows the BIOS too so maybe you have a diff bios ?
check the positions of JP37, JP38, JP39, JP40, RN8 for volts. AND ...for CPU : RN5, RN6, RN7, JP20, JP26, and JP42, JP65, JPX1, JPX2.
CPU Speed is JP27, JP28, JP29.
Attached some pictures and here is the link https://aukro.cz/retro-hw-abit-ab-pw4-amd-486 … adic-7041206133
someone else with have to help for any more cause I need to go right now.
edit: added your board cpu section

Horun wrote on 2024-10-03, 02:22:

Here are some pictures from Aukro.cz that show same board running an AMD DX4-100, shows the BIOS too so maybe you have a diff bi […]
Show full quote

Here are some pictures from Aukro.cz that show same board running an AMD DX4-100, shows the BIOS too so maybe you have a diff bios ?
check the positions of JP37, JP38, JP39, JP40, RN8 for volts. AND ...for CPU : RN5, RN6, RN7, JP20, JP26, and JP42, JP65, JPX1, JPX2.
CPU Speed is JP27, JP28, JP29.
Attached some pictures and here is the link https://aukro.cz/retro-hw-abit-ab-pw4-amd-486 … adic-7041206133
someone else with have to help for any more cause I need to go right now.
edit: added your board cpu section

Woow, thanks a lot, it is the same board as mine... I will try when i will come home from work, and let You know....
Thanks a lot

Hehe, couldn't resist, came home for "lunch", and tried this settings - It worked!!!!!!! CPU is set as 120MHz (maybe because i have flashed this new BIOS mod from 2024), but it worked OK so far. Bad thing is that it work only on one VGA card (8bit ISA), i need to test others on other systems (one VLB, one 16bit ISA doesn't work).
Thanks a lot, will let You know outcome when i get back from work 😀

No, no other VGA card except one 8bit ISA doesn't work on this MBO!!! I'm erasing the eeprom and i will try to program "normal" BIOS on it. If this won't work, i don't know what could be the problem....

Nope, same thing with E2 BIOS also!
What could cause this mess? Only 8-bit ISA VGA card works! VLB cards causing BIOS error beeps (1 long 4 short), and i tried this GC on other system, it worked perfectly!

120Mhz cpu ? Sounds like the motherboard is running the BUS at 40Mhz (is why 120Mhz cpu instead of 100Mhz). You need to make sure BUS is at 33Mhz, you are currently overclocking the cpu and probably the ISA and VLB bus.
Some VLB video cards can work at 40Mhz but need added wait states which are by jumpers...JP9 and JP10. Both should be jumpered...
Please post a picture of your JP27, JP28 and JP29.

I agree with Horun, it totally sounds like your bus speed is incorrect (too fast).

Hi, thanks for an answer.
Yes, JP9 and 10 wasn't jumpered, i have done it now, but it is still at 120MHz. Here is the pic with jumper 27, 28,and 29.... Probably the answer is here 😀

I changed JP27 from open to close, now the CPU speed is 100MHz, but still, only this VGA card is working, VLB doesn't 🙁

Hmm pull the jumper off JP5, that is the video card/monitor type. You generally want it set to Mono for a VGA card. Other thought: maybe the 14.3Mhz ISA clock signal is not working proper....some cards need it

I pulled out the JP5 - same thing! This 14.3Mhz clock signal, does it have have something with the round oscillator near JP14? This one was "green as hell", from the battery acid damage 😀 If not, what should i check to see if the clock is ok?

Yes the little round 'can' crystal by JP14 is the ISA "OSC" 14.3Mhz crystal. If that is not working then most ISA cards that need that signal cannot clock or sync to the motherboard properly.
Best way to check is with an oscilloscope at the ISA slots (check ISA pinouts, is B30 iirc). You never mentioned you had a lot of corrosion before.

Horun wrote on 2024-10-05, 02:43:

Yes the little round 'can' crystal by JP14 is the ISA "OSC" 14.3Mhz crystal. If that is not working then most ISA cards that need that signal cannot clock or sync to the motherboard properly.
Best way to check is with an oscilloscope at the ISA slots (check ISA pinouts, is B30 iirc). You never mentioned you had a lot of corrosion before.

Yes, it was green, but i "wash" the board in vinegar (over night 1:3 Vinegar/distilled water), desolder RTC socket and keyboard connector, and fix the connections that were bad. Other traces i have checked for continuity, and all seems ok so far.
I don't have an oscilloscope, so i guess there is no other way to check?
I could only check for voltages (5, -5, -12, 12 V), and they were all fine (Pins B3, 5, 7, 9). Voltage i get on this B30th PIN is around 1,9V.

I didn't ask one question! If i connect 8bit ISA Graphics Card into "first part" of 16bit ISA slot, will it work? I'm asking because, when i connect that only working 8bit ISA card into those other slots (16bit and VLB), it beeps like those other cards?!?

That board has a whole lot of Winbond. Too bad the CPU isn't Winbond too.
How's the performance of this board?

Anonymous Coward wrote on 2024-10-05, 13:04:

That board has a whole lot of Winbond. Too bad the CPU isn't Winbond too.
How's the performance of this board?

Hi,
couldn't test it because i cannot find ide isa card that works! Or maybe those 16bit isa and vlb slots doesn't work at all?