Member Avatar for spiro1263

I recently built a new pc which was running fine for a couple of weeks without any problem. I then didn't use the computer for 2 weeks.

When I next came back to use it, I pressed the on button, it started for a second and then stopped. It then repeated this process every 4 or 5 seconds without me touching the on button again.

I opened the case up. The green mobo LED is on. On trying to start, all the fans spin for a second and then stop.

I have tried removing/swapping various components with another PC I own. From this I have determined that it is not the graphics card, memory, hard drive, optical drive or PSU. I also have deduced that it’s nothing to do with the case on button or reset switch.

I have also checked all connections and even re-seated the heatsink to no avail.

Before I go out and change the mobo or CPU, does anyone have any further ideas?

My spec is:

Intel Core 2 Duo E6550
Asus S775 P35 motherboard
7900GTX Graphics Card
2GB Ram
Akasa 500W PSU

Thanks

Mike

  • 3 Contributors
  • 6 Replies
  • 2K Views
  • 22 Hours Discussion Span
  • Latest Post Latest Post by willcomp
Houssem Eddine commented: When I pressed the on button, it started for a second and then stopped. It then repeated this process every 4 or 5 seconds without me touching the on +0

Dani AI

Generated

Nice catch, . What you saw is different from the brief, one-time power cycle many P35 boards do after AC is restored or hardware/BIOS settings change (as noted). A rapid 1-second spin-up/1-second off loop usually means POST never starts because saved CMOS values are bad or a hardware protection trips. Pulling the battery let the RTC/CMOS fully discharge, which cleared those values.

For next time, use the board’s CLRTC jumper instead of waiting hours with the battery out. It does the same thing, just faster and more thorough because it hard-shorts the CMOS rail. Safe sequence:

  • Power down, switch the PSU off, and unplug it. Press and hold the case power button for 10 seconds to drain flea power.
  • Move the CLRTC jumper from pins 1-2 to 2-3 for 10–15 seconds (or short the two clear pins with a screwdriver if there is no cap), then move it back.
  • Reinstall the battery, plug AC back in, boot, and immediately Load Setup Defaults. Re-set date/time, SATA mode (AHCI vs IDE), and boot order.

If the loop returns, work through these quick checks:

  • Verify the 4-pin/8-pin CPU power plug is fully seated; a loose EPS12V often causes instant shutoff.
  • Inspect for an extra case standoff shorting the board and for any bent LGA775 socket pins.
  • Seat RAM firmly; test with one module in the slot the manual recommends for single-DIMM.
  • Connect a small case speaker to the front-panel header so you can hear beep codes; no beeps can simply mean no speaker is attached.
  • Once stable, consider a BIOS update only if the release notes mention cold-boot/POST fixes.

And for Windows-level restart loops (different issue), ’s advice applies, or use F8 at boot and choose "Disable automatic restart on system failure" to catch the stop code.

Recommended Answers

All 6 Replies

Member Avatar for willcomp

P35 chipset mobos start for a few seconds, turn off for a few seconds and restart on initial boot. BIOS plays a role in this behavior.

Try resetting CMOS. A BIOS update would probably help, but appears you probably can't boot from a floppy to flash BIOS.

Member Avatar for 4th&3wood

You can stop the restarting by going to Start> My Computer> Properties, click on the Advanced tab, then Settings, then Startup and Recovery. Under System Failure uncheck the Automatically Restart box, click on OK.
This should allow you to see any error that is appearing when you first start the computer. Please post that back here.

Member Avatar for spiro1263

Thanks for your replies.

Willcomp - I will try resetting the CMOS to see if it makes any difference. I also read on one forum that it does this if the battery is dead - but I'd be surprised if it was dead when it was presumably fine only two weeks earlier.

4th&3wood - I can't get into XP to change this setting as the computer effectively switches off 1 second after starting.

There are no warning beeps on starting either. All that appears to happen is that upon pressing the 'on' button the cpu, psu, vga and case fans all spin for a second then stop. Nothing else happens (i.e. hard drive doesn't spin, no vga display etc.) Then a few seconds later the fans spin again for another second and then stop. . . this process then repeats and repeats.

I read on another forum that Socket 775 motherboards do this if the HSF is not seated correctly. I checked this by re-seating the HSF but it hasn't made any difference.

Thanks

Mike

Member Avatar for willcomp

If CMOS reset doesn't work, it wouldn't hurt to try another CMOS battery just in case yours is faulty. They are cheap and easy to replace. Available at Wal-Mart and Radio Shack (CR2032 coin cell).

Since motherboard is rather new, a dead battery would not be expected.

Member Avatar for spiro1263

Success!! - I've got it working!

I took the battery out and left it out. When I came back to it a couple of hours later I popped the battery back in, switched it on and it worked. Thanks to Willcomp for suggesting this!

I'm still a bit of a novice when it comes to building computers. So any chance of someone answering these questions:

1. I presume taking the battery out reset the CMOS? If so what is the purpose of the jumper which the mobo manual says is for clearing the CMOS - I've not touched this jumper.
2. Why did the CMOS need to be reset in the first place when the computer had worked fine for two weeks since building it?

Many thanks.

Mike

Member Avatar for willcomp

Success!! - I've got it working!

I took the battery out and left it out. When I came back to it a couple of hours later I popped the battery back in, switched it on and it worked. Thanks to Willcomp for suggesting this!

I'm still a bit of a novice when it comes to building computers. So any chance of someone answering these questions:

1. I presume taking the battery out reset the CMOS? If so what is the purpose of the jumper which the mobo manual says is for clearing the CMOS - I've not touched this jumper.
2. Why did the CMOS need to be reset in the first place when the computer had worked fine for two weeks since building it?

Many thanks.

Mike

1. Yes, removing battery clears CMOS. The Clear CMOS jumper does the same thing. CMOS is volatile memory and flushes when power (battery) is removed. CMOS is powered from 3.3VDC when PC is on.

2. Stuff happens. CMOS can become corrupt at any time.

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.