VOGONS


First post, by dormcat

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I've got a system from an e-waste recycler: Asus P4C800 Deluxe + P4 HT Northwood 2.8 GHz + 2048 MB DDR (4 x 512) + ELSA Fire GL X2 256 MB + SB0220 + three HDD (40 GB PATA, 80 GB PATA, and 80 GB SATA).

Other than the ultra-heavy chassis and the ELSA Fire GL X2 with tons of "snowflakes," the floppy drive and three HDD were working, and MemTest86 showed no error on the four 512 MB DDR strips. I was about to give it a quick install of Windows XP when suddenly the system gave me "Overclocking failed! CPU Over Voltage Error!" warning. The CMOS battery was long dead so all BIOS options should be default values. The hardware monitor showed VCore with red font: 1.008V only. I replaced the PSU with two other ones but the problem wasn't going away (i.e. the problem might be on either MB or CPU). Worse yet, the startup became very unstable: only about 50% times can shown POST, while the other 50% would give me a blank screen i.e. fans were spinning but no display. I also noticed that starting up after long-time power off would not POST, but if I turned it off a few seconds and turn it back on then it would POST normally (for the record, the reset switch didn't work under any circumstance).

I searched the web but found no useful info. I even managed to update the BIOS from v1011 to v1019 (some said updating BIOS might fix the problem; even Asus claimed v1014 "fix the system hangs after clear CMOS") with a floppy but nothing helped.

The MB offered manual VCore adjustment but there's another problem:

  • BIOS offered VCore from 1.525V to 1.950V
  • Intel's website lists VID Voltage Range from 1.250V to 1.400V
  • Wikipedia lists VCore from 1.475V to 1.525V

I'm really hesitant to adjust VCore manually this way, as the incorrect voltage could damage the CPU and/or the MB.

My questions:

  1. What's the possible cause (capacitors, MOSFET, etc.)? Could it be fixed without soldering and replacing components?
  2. Does the low VCore have anything to do with the 50% successful POST?
  3. Is it safe to adjust VCore manually to 1.525V with BIOS?
  4. What if I simply ignore the error message and run the system with low VCore?

Thanks in advance.

Reply 1 of 5, by dominusprog

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1. Caps are the main suspect, what’s the condition?
2. Yes, it can be.
3. No, besides it probably doesn't fix the problem.
4. Well, the computer will become highly unstable.

The latest BIOS version is 1023. How did you update your BIOS?

https://www.asus.com/us/supportonly/p4c800-e% … /helpdesk_bios/

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Reply 2 of 5, by dormcat

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dominusprog wrote on 2023-09-07, 12:16:

1. Caps are the main suspect, what’s the condition?

They look fine from the exterior; no bulging or leaking. The only testing tool I've got is a simple entry-level multimeter without capacitance test, and my soldering skill is rudimentary at best.

dominusprog wrote on 2023-09-07, 12:16:

The latest BIOS version is 1023. How did you update your BIOS?

https://www.asus.com/us/supportonly/p4c800-e% … /helpdesk_bios/

I'm afraid that the MB is a P4C800 Deluxe, not the P4C800-E Deluxe you linked. The last stable BIOS is 1019 while the beta BIOS was 1021.005; I used Afudos BIOS update tool V2.26 provided on the download page to update BIOS with a DOS floppy and it went through smoothly.

The attachment IMG_20230908_055919.jpg is no longer available

For the record, Asus did not print "Deluxe" on the PCB; it could only be identified with the additional Promise PDC20378 controller chip and the additional PATA + 2 SATA ports accompanied it.

Reply 3 of 5, by Karbist

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There are 3 zero ohm resistors on the vcore feedback line near the pwm ic that you can measure with your multimeter:

The attachment Asus_P4C800_Deluxe_F.jpg is no longer available

Reply 4 of 5, by CharlieFoxtrot

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dormcat wrote on 2023-09-07, 21:48:

They look fine from the exterior; no bulging or leaking. The only testing tool I've got is a simple entry-level multimeter without capacitance test, and my soldering skill is rudimentary at best.

Capacitors may very well fail without any external signs. This board is from the worst era of capacitor plague and especially cheap low-esr caps manufactured by several Taiwanese companies and used on the VRM were often very poor quality because of unstable electrolyte chemistry. Many of these type of caps failed already back in the day after a year or two of normal use. Bad caps on the CPU VRM would explain anomalies or unstability of Vcore, so I wouldn't count off the caps just based on how they look. And to measure these caps reliably, you pretty much need to do it off the circuit which means that for the same effort you pretty much do a recap anyways.

Reply 5 of 5, by dormcat

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Thanks to everyone for the advice. Guess it's not worth the extra efforts for a system isn't even mine; I'll leave it to the owner to decide its fate.