Motherboard or CPU?

[crowndale]

I've had a home-built PC running since January with an ASUS P4P800 motherboard & a 3Ghz Pentium 4 processor, and until recently it was fine. About a week ago Windows XP closed itself down for no apparent reason a couple of times, then a few days later it got to the point that the machine would shut down & reboot every few seconds, not even getting any display to the monitor.
Took it apart and found that all fans came on when the power applied to the system (start button not pressed) but just for a few seconds then, after a few more seconds, the process would repeat about 3 times. Pressing the start (power on) button would trigger the same process with the same result.
Took motherboard out of case and tried with everything apart from RAM & processor removed - same result. Bought new power supply - same result.
There are no beeps, even with RAM removed it's exactly the same.
Tried with video card installed, and about once every five attempts I briefly see the ASUS splash screen before the system shuts down again.
Help - please!!!! It can only be, I think, cpu or motherboard but which?

 

[Igorian]

A couple of things to try. Reset BIOS to fail safe defaults. Try using other memory, or if using two sticks, just try each one separately. There is a BIOS update which fixes the absence of beeps when no memory installed.

 

[nstreet]

If the BIOS reset as suggested doesn't work, it could be either. I had a simliar problem a year or two ago with the system repeatedly shutting down for no apparent reason, turned out to the be power supply!

If you have to go down the 'suck it and see' route, a motherboard is about £50+ a CPU is going to be upwards of £150. If you have friends who have similar systems, see if you can test the cpu in theirs. Good luck.

 

[crowndale]

Thanks for the tips, guys.

I can't reset the BIOS via software as I can't get the PC to stay alive for that long, but I have taken out the battery & reset the values using the jumper but it didn't help. I've also tried with both sets of memory sticks, only one set, and no memory, in various combinations of slots - still no joy. I did apply the latest BIOS update about 2 weeks ago.

I've also bought & tried a brand new power supply - no joy; same symptoms!

I've just got back from PC World to get some thermal compound but they've sold out! Trying another cpu would be good, but finding someone willing to take out their Pentium 4 for me to try would be difficult!

 

[Igorian]

Where do you live Crown? We have the ability to test MB/processors.

 

[ZenStalinist]

Yeah, could be either.

Also, check the motherboard is fully stood off the case, it could be shorting.

I also had this problem back in '99 with a Time PC. It did this a few times and then refused to boot, but the fan spun 'round. I believe at first they suspected either the BIOS or the CPU. I think they may have replaced the CPU, though I can't really remember.

Did you buy your motherboard and CPU from the same vendor? If so, then they tend to be quite good if you send them both back, and they will often sort it out for you.

Who did you buy it from?

 

[crowndale]

I live in Bristol, where are you Igorian?

I have taken the motherboard out of the case and the problem's the same. It was bought from Aria in January together with case, HDD, RAM & Windows XP. At that time they didn't have the processor in stock so I bought it from Dabs.com.

I have contacted Aria claiming a faulty motherboard and they've now issued me with an RMA number. I'll removed the processor etc today and should have some thermal compound by tomorrow so I'll try re-seating it. If that doesn't work then it'll be winging its way to Aria where, hopefully, they'll find it to be faulty.

Peter

 

[Igorian]

Unfortunately, too far to pop over.(I live in Northants). We use a post probe to test motherboards. It will show status codes for all but the really dead motherboards.

I guess you did plug in the four pin 12V connector? (You never know!)

 

[crowndale]

Thanks anyway, Igorian, kind thought. Also, four-pin connector is well & truly connected.
I'll let you know what the final result is!
Peter