This happens with a standard 84MB Conner HDD (which should be at least compatible with the motherboard)

This seems to be quite an old VOBIS BIOS for this board.
Have you tried the latest FIC BIOS?

majestyk wrote on 2023-01-07, 06:15:

This seems to be quite an old VOBIS BIOS for this board.
Have you tried the latest FIC BIOS?
2106c800.zip

After some looking around and checking the mentioned bios.. I red the included TXT file.. It says that the bios is ment for a PCB 1.32 version.. Which mine is PCB version 1.2
Bios 25c800 seems to be the most reliable for this motherboard.. But non of them seems to give me a stable working motherboard.

After some Deoxit D5 threatment of the whole board (first sprayed in the expension slots (pci and isa) which fixed a lot of throubles with my graphic cards. (also the cards those where looking death are working again)
Then sprayed everything in which could be corroded over the last 30 years. Took a tooth brush and softly brushed he connections of the QFP chips.. And IDE headers and so on..

After that.. Tried the board again.. Like i said the problems with the graphics cards went away.

I have got the board running on the floppy drive for 3 times. Could boot up a floppy and ended with an A prompt.

After that the board is very unstable. Tried every eeprom with different rom.. Load bios settings, checked if settings where disabled or enabled.

Often the board hangs on the floppy drive.. Floppy drive is first spinning normally.. After that the drive wont make a normal booting sound anymore , but still spins a constant RPM and light keeping on. . And systeem looks like it hangs..
Then reset the system.. Then also hangs often on AUTO detection on the first pass on the primary drive.. If there is no drive attached.. Normally it would skip that pass and go on.. But now it just hangs on the first try..

What i also found out is that from bios version 2160c800 it wont show a memory bank setting anymore.

There is a setting in the bios, where you can set each bank from STANDARD (FPM mem) to EDO)
Version 25c800 shows the banks from 0, 1, 2 (because there are 3 banks on my board) version 2160c800 only shows me bank 0 and 2 in the bios.

But the problem now is, the board is very unstable..

I might consider a recap for this motherboard..

My main question is.

There is a VRM on board. It has two settings. Will the VRM always (in any circumstances ) be used.
Could it be if the big cap is dried out ( of the VRM) that it doesnt provide any clean current to the motherboard, and which will be unstable then?

Also might consider to go with a newer PLCC style eeprom.. The Eeproms which iam using now are old stock which iam bought from ebay. They write an read just like normal.
I dont know old the are... But should be from 1993 / 1994 which the seller mentioned in his action list.
Could this maybe the coulprit?

Robin4 wrote on 2023-01-13, 16:10:

[...] […]
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[...]

But the problem now is, the board is very unstable..

I might consider a recap for this motherboard..

My main question is.

There is a VRM on board. It has two settings. Will the VRM always (in any circumstances ) be used.
Could it be if the big cap is dried out ( of the VRM) that it doesnt provide any clean current to the motherboard, and which will be unstable then?

Could be. Have you measured the voltage output of the VRM yet? What did you measure?

Those settings are probable VS and VRE. Which are you using?

Also might consider to go with a newer PLCC style eeprom.. The Eeproms which iam using now are old stock which iam bought from ebay. They write an read just like normal.
I dont know old the are... But should be from 1993 / 1994 which the seller mentioned in his action list.
Could this maybe the coulprit?

Highly unlikely. You're not getting BIOS checksum errors, your BIOS is loading fine, it's just having (firmware) issues with your board hardware.

Bad contacts at jumpers?
Bad RAM-socket contacts?
Loosened solder joints at chipset pins?
Cracked resistor array?
Have you tried with all cache- and TAG-chips removed? Are the cache voltage jumpers set correctly?

Thanks all, Good suggestions here.

No iam no yet did the measurement on the voltage on the out put of the vrm jet.. But i now have the time, so i will do in a few minutes.

Can you tell me which pin is the output of the vrm... Only knows about base, collector, emittor. But only dont know what it do or how it works.

CPU is now set on 3.3volt (jumper j15 is set, the other option is j16 which will give 3.5 volt.

Firmware issues could be.. Every version above 25c800 didnt work withouy any troubles.

Bad contact at jumpers?

* Can do i check if nothing will help, but for now the jumpers looks normal installed and no defective or broken jumpercaps.

Bad ram socket contact?

*The look just normal and memory seems to work fine.

Loosened solder joint at chipset pins?

* Didnt used a sharp pick to try it out.. But with cleaning with deoxit d5 and toothbrush i kept my eyes on them to see anything moving when clean.. (if after nothing would help maybe consider to reflow the legs of the QFP chips. but for now
i dont want to damage the board in the short run..

Cracked resistor array?
*Resistors look normal on the eye. (and al the resistor arrays looks normal)

Have you tried with all cache- and TAG-chips removed? Are the cache voltage jumpers set correctly?

*Earlier i replaced the onboard cache chips 256K with other good working chips for 512K of cache.. so the old chips where removed. But yesterday i also sprayed on top of the legs with deoxit d5 (dont know if it will flow through the legs in to the socket, but iam guessing it will. But i can re-do it a second time. But strange is the cache is just working fine.. It will be detected by the motherboard and bios. And yes everything is set correctly.. Iam guessing these cache chips are just 5 volt parts. I know there are 3.3 volt chips also.. But they are mostly newer.

The installed cpu is a A8050290 sx968 (pentium 90 ceramic)

https://www.cpu-world.com/sspec/SX/SX968.html Core voltage as it says 3.3 volt.

I did the measurement on the VRM..

The emitter measures 4.99 volt.
The collector measures 3.33 volt exact.

So that should work fine. As there is no voltage drop.

Is there a way to do an inline capacitor test?

Like to know if the big one on the VRM is good or bad.

anyone have other suggestions?

Thinking of disable onboard IDE and floppy controller. So can try a external ISA card instead.

I bought a new motherboard.. And this one is working.

Back on my new board.

I swapped the cache chips on those.

Went from 256kB to 512KB

I installed 512ak chips.

I can set my board to 3.3 volt or mixed mode.. Which one do i set?

Iam guessing these winbond srams arent 3.3 volt?

Some help i found here:

feipoa wrote on 2022-11-11, 15:10:

Bummer about the *245 buffers. Would I need to de-solder them if installing PB SRAM? […]
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Bummer about the *245 buffers. Would I need to de-solder them if installing PB SRAM?

Good news about the jumper block being unpopulated.

There's another set of jumpers, which I may need to alter. See photo.
Asus_JP8_thru_JP11.JPG

It looks to be setting the voltage for the SRAM. My board has JP8 and JP9 soldered closed. The board calls this "MIX SRAM". Then there's JP10 and JP11 which are left open and the board calls this 3.3V SRAM. It is not clear to me if "MIX SRAM" is only for mixed-mode SRAM (supply voltage is 5V, but output level is 3.3 V), or if it is also for 5 V SRAM modules, or both options (hence the 'mix'). What do you guys think? I'm using traditional 5 V SRAM in my board now. Was I supposed to use mixed-mode? I'm pretty sure the RAM in this board, when I bought it, was standard 5V.

In either case, the pipeline burst SRAM modules use 3.3 V, so would I need to adjust this as well? I am unable to determine from that photo provided by majestyk which jumper bar is soldered in which jumper locations.

Regarding which size TAG to use, the Asus manual states that I can use either 8k8, 16k8, or 32k8. As such, I would continue to use the 32Kx8 that I currently have installed.

It wasn't clear to me from that 430FX datasheet if two pieces of 64kx32 is supported for 512KB PB SRAM, or if I had to use four pieces of 32kx32. I suspect the latter. Nonetheless, I a 64kx32 chip would use pin 49, which is Address A15, while on a 32kx32 chip, pin 49 is N/C. So I looked at the traces on the Asus board for Pin49, but it appears not to be connected. Thus I am limited to 256K PB SRAM on this board.

So i guess mixed mode it is.

Also compared the old board with the newer one.. Seems to be the newer one has the two tantalum capacitors replaced.
Think thats going to do next with the old board.

Maybe there something more wrong, at least this is a start to begin with.