troydm wrote on 2026-06-27, 17:22:

Got ASUS P/I-P55T2P4 rev 3.10 motherboard on power on Post code C1 memory not detected is shown, no matter if ram sticks presen […]
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Got ASUS P/I-P55T2P4 rev 3.10 motherboard
on power on Post code C1 memory not detected is shown, no matter if ram sticks present or not it just repeats long beep and post card C1 code.

What I did and it didn't helped:
Recapped all capacitors
Checked most questionable traces and they are okey
Cleared CMOS
Tried bunch of different ram sticks in different configurations both FPM and EDO

No Tag ram IC is installed

Any suggestions what to check more?

Tried pressing down the HX chip?
Checked all legs of the other one?

Nexxen wrote on 2026-06-27, 17:45:

Tried pressing down the HX chip?
Checked all legs of the other one?

yes, tried pressing all chips and checked all legs, nothing out of place and soldering looks solid so definitely not a problem, and they don't overheat

also would like to check memory slot voltage rails, but I am not sure which values and pins should I look for, it's 72 pin simm memory slot

troydm wrote on 2026-06-27, 21:59:

Nexxen wrote on 2026-06-27, 17:45:

Tried pressing down the HX chip?
Checked all legs of the other one?

yes, tried pressing all chips and checked all legs, nothing out of place and soldering looks solid so definitely not a problem, and they don't overheat

also would like to check memory slot voltage rails, but I am not sure which values and pins should I look for, it's 72 pin simm memory slot

https://en.wikipedia.org/wiki/SIMM

+5V

It's boring stuff to do, it'll take time and maybe bore you to death. Soldier on! 😀

Check the clock signal at the RAM slots
and
reflash BIOS.

troydm wrote on 2026-06-27, 17:22:

No Tag ram IC is installed

According to the jumper manual on TheRetroweb, the only valid configuration without Tag RAM is one with a COAST module with Tag RAM installed.
Do you have a COAST module with Tag RAM installed?
Have you tried installing the 32Kx8 Tag RAM?

Dorunkāku wrote on 2026-06-28, 11:36:

According to the jumper manual on TheRetroweb, the only valid configuration without Tag RAM is one with a COAST module with Tag […]
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troydm wrote on 2026-06-27, 17:22:

No Tag ram IC is installed

According to the jumper manual on TheRetroweb, the only valid configuration without Tag RAM is one with a COAST module with Tag RAM installed.
Do you have a COAST module with Tag RAM installed?
Have you tried installing the 32Kx8 Tag RAM?

Version 3.1 of this mainboard does not have a COAST-slot. It comes with full featured 512K cache and a soldered TAG-RAM. The 2nd TAG -RAM in the DIL28 socket _can_ be populated, if a cacheable area of 512MB is desired.

My biggest suspect is some trace broken somewhere, ultra boring chipset - ram sockets continuity test is unavoidable.

I´m afraid this continuity test is impossible to do, because the HX-MCH´s BGA soldering pads are hidden unterneath the chip and cannot be accessed. What can be done is check address lines and data lines of the RAM slots with a ohmmeter against ground to (indirectly) verify their connetctions to the respective output circuits of the chip.

majestyk wrote on 2026-06-28, 16:58:

I´m afraid this continuity test is impossible to do, because the HX-MCH´s BGA soldering pads are hidden unterneath the chip and cannot be accessed. What can be done is check address lines and data lines of the RAM slots with a ohmmeter against ground to (indirectly) verify their connetctions to the respective output circuits of the chip.

True, my mistake. It's a HX not FX.
Guess I have to go somewhere fresh to de-boil my brain 😀

majestyk wrote on 2026-06-28, 16:58:

I´m afraid this continuity test is impossible to do, because the HX-MCH´s BGA soldering pads are hidden unterneath the chip and cannot be accessed. What can be done is check address lines and data lines of the RAM slots with a ohmmeter against ground to (indirectly) verify their connetctions to the respective output circuits of the chip.

to be clear I understand you correctly, I need to check each address and data line with multimeter against vss pin (ground according to pinout), and if there is resistance of 100 something ohms then it's Okey, if it reads 0 then something is definitely broken?

troydm wrote on 2026-06-28, 21:54:

to be clear I understand you correctly, I need to check each address and data line with multimeter against vss pin (ground according to pinout), and if there is resistance of 100 something ohms then it's Okey, if it reads 0 then something is definitely broken?

More likely scenario is reading infinite resistance.
Measuring resistance you should be able to detect clamping diodes in the chipset. This is how those funny cpu and ram "socket testers" work.

I wasn't all that boiled, I have the board without the HX chipset.
Traces are traceable (pun intended), as there are testing points.

I'll provide a wider picture later for future reference.