Skyscraper wrote on 2023-04-20, 11:44:

I kind of doubt it's the caps as they look fine and rarely go bad on late Asus s478 boards. […]
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I kind of doubt it's the caps as they look fine and rarely go bad on late Asus s478 boards.

In my experience BIOS (chip) issues like mentioned if the board powers on, shorted mosfet/mosfets in the CPU VRM circuit if it dosn't.

If the boards powers on and you have already replaced/reflashed the BIOS then keep the board powered on for a few hours. If it's the caps they might be persuaded to start working enough to let the board post.

Other things to try.

Another PSU like mentioned, especially if the board dosn't power on.
Other memory even if the memory used is known good.
Another video card.
Getting a POST-code card to see if there are any codes that could indicate where the issue is.

I think it's just some of the black OST caps on his board, those have a nasty tendency of looking great and being pretty 50/50 on actual capacitance. Agreed to rule everything else out before a recap.

ODwilly wrote on 2023-04-20, 12:03:

I think it's just some of the black OST caps on his board, those have a nasty tendency of looking great and being pretty 50/50 on actual capacitance. Agreed to rule everything else out before a recap.

Could be but they need to be really bad to keep the board from posting.

I hate when you don't know for sure and I rarely try to recap boards that aren't posting unless its an almost certain that the caps are the culprit. It's much better when you have a posting but flaky motherboard with bulging caps! 😁

PcBytes wrote on 2023-04-20, 09:46:

chinny22 wrote on 2023-04-20, 09:26:

Socket3 wrote on 2023-02-16, 17:09:

Asus P4P800 (especially the E and SE) is known for EEPROM chip / bios and some other issues. If you have an EEPROM writer, take the chip out and re-flash it. Better yet, replace the chip with a winbond of the same capacity, flashed with the correct bios. Even better, launch it off a trebuchet as posted above, and find an Abit AI7 or IS7. If you really want to stick with Asus, try sourcing an Asus P4C800, they're pretty solid.

Do you know why that is? Indeed i've a SE which luckily does turns on just to tell me I've a corrupt BIOS
Only PC i've had that's done it

Corroded pins on BIOS chip very likely. I have a P4P800-E Deluxe here that needed a new BIOS chip just because the original one looked rotten as all hell.

@Socket3 - I wouldn't really rely on IS7 either. While better than the P4P800, these also had issues with their BIOS chips, from what I remember, albeit at software level (BIOS would corrupt itself, from what I remember from my BE6-II) though I wouldn't take a dying BIOS chip off the list.

BE6-II and BH6 yeah, I've had problems with these boards nuking the BIOS myself, but it only occurred during overclocking sessions. The IS7 is rock solid. I've had several, and apart from capacitor issues (common to all boards from that period) I've never had one die on me. The IS7 I'm using at the moment I've owned since 2006 and it's been through countless configurations and systems throughout the years. My backup IS7 was pulled from a scrap pile at a recycling center. It was partly covered in mud - gave it a bath, replaced one of the memory sockets and it's been reliable ever since.

The P4P800 physically damages the eeprom. I don't know if it's a problem with the board or the EEPROM itself - I'm leaning towards the latter, since all board's I've repaired with another bios chip (I used a winbond chip instead of the stock atmel) are still going. I'm guessing Asus got a bad batch of EEPROMs, but can't confirm.