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Dead motherboard? Won't POST

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  • Motherboards
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May 21, 2011 10:05:10 PM

Hello, I bought Gigabyte P67A-UD4 because my previous ASUS fried and I could not wait for a replacement to arrive. I hooked up a bare system (MB+CPU+RAM+VGA) in a testbed and it POST fine (short beep) but I couldn't get into BIOS. Whenever I pressed delete to enter BIOS it immediately resetted. When I didn't press any key, it would reset shortly after the beep anyway. So I unplugged power cord and cleared CMOS. After I done that, it wouldn't even post. Fans just spin on, and computer shuts off and on in cycle until I turn PSU off.

I removed all components and assembled it again to reseat it, but no dice. Is this motherboard DOA? On my previous board a 4pin 12v ATX connector melted, so I replaced PSU and motherboard for new to test whether the CPU survived or not.

If it didn't post at all I would have guessed it's a dead CPU, but after seeing it successfully POSTed at first and now it doesn't I not so sure whether it's MB or CPU :/  What do you guys think?

More about : dead motherboard post

a b B Homebuilt system
a b V Motherboard
May 21, 2011 10:13:47 PM

I have the same board, when attempting to enter bios did you spam delete key or just hit it once? Gigabyte seems to have an issue where double hitting delete resets the computer. The f3 bios I think is supposed to fix it. Did you also try removing the battery from the motherboard and trying to get it to post? Also had that problem when tweaking my voltages and timings to get an infinite reboot loop and using the cmos reset pins didn't work only the battery would cause a reset. Although you didn't do anything to need to reset it but nevertheless might fix it. The boards are fun like that.
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May 21, 2011 10:19:16 PM

I removed battery for good 4 hours. Didn't work. It looks totally dead after I attempted Clear CMOS.

And yes, I spammed DELETE key, which might caused the reset. But still when I didn't press anything board resetted 2 seconds after beep. No "disk error, no drives found" or anything. Just that white splash screen -> reset, splash screen -> reset.
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a b B Homebuilt system
a b V Motherboard
May 21, 2011 10:26:16 PM

Do any of the LED lights by ram slots light up? When I had the issue similiar to yours my fans turned on the hsf started to spin and then the hsf turned off and a few seconds later the computer rebooted and just cycled...it only took the battery coming out for me to fix that if your LEDs aren't on that would indicate cpu failure otherwise it could be the mobo.
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May 21, 2011 10:32:33 PM

Phase leds (about 6 of them, making a straight vertical line)? Yes, they light up every time. I was thinking maybe a BIOS chip is faulty, but then again that was just my guess, I never experienced such issue until now.

To tell the truth I have had only troubles so far with the Sandy bridge series. My previous build Q6600 was and is rock solid. :(  I'm quite disappointed to be honest with Sandy Bridge stability (performance was perfect when it worked though). But that may be just bad luck.
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a b B Homebuilt system
a b V Motherboard
May 21, 2011 10:38:28 PM

Ya the P67 boards have been a hassle...first the cougar point fiasco and even the B3 models have their quirks. You could try z68 and hope that they aren't as much of a problem for you but who knows what issues lie waiting to be discovered. Gigabyte has the dual bios feature as well...even if you screwed up the bios it should still let you get into the 2nd one...I'm out of options from my end >.<
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May 21, 2011 10:45:02 PM

I thought about it as well - Dual BIOS. But As far as I understand it's automated to switch to second BIOS. What if BIOS 1 "thinks" it's ok, but it in fact isn't?

If it was possible to force load from backup BIOS, it would've been much easier to rule it out.
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a b B Homebuilt system
a b V Motherboard
May 21, 2011 10:50:57 PM

Or it's another issue. From what I understand if the bios is corrupt, it loads the backup and copies the back up to the main bios and then reboots using the main bios. If there is still a hardware issue preventing it from booting it will just keep cycling.
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a b B Homebuilt system
a b V Motherboard
May 22, 2011 10:35:27 AM

I believe a bad CPU is your problem.

Take your video card out and see if you get a whole bunch of beeps, if no beeps this of course leaves out the VIDCARD, but does not leave out the CPU/MOBO. If you get beeps, take out the RAM, you should get a long growling beep from the RAM being out.

If you do get beeps after taking the RAM/Vid card out take note of the beeps and try to figure out what they mean(google beep codes).

In my experience however, no beep codes means dead CPU, 9 times out of 10. Sometimes bad mobo/psu thou.
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May 22, 2011 10:38:16 AM

Sure it can be dead CPU, but why it POSTed at first and then nothing after BIOS reset? I took out everything, just mobo+cpu and no beep codes.
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a c 122 B Homebuilt system
a c 156 V Motherboard
May 22, 2011 12:09:40 PM

Bad CPU's are extremely rare. More likely it is the PSU or motherboard. What are your complete system specs?

Troubleshooting ideas ...

Work systematically through our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-postin...
I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

If not, continue.
The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

Breadboard - that will help isolate any kind of case problem you might have.
http://www.tomshardware.com/forum/262730-31-breadboardi...

Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

Make sure you plug the CPU power cable in. The system will not boot without it.

I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

If no beeps:
Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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May 22, 2011 12:38:21 PM

Thanks for your answer jsc, I already went through that troubleshooting FAQ. I currently have:

CPU Intel 2500K
MB Gigabyte P67A-UD4 stepping B3
MEM A-Data XPG Gaming Series V2 2x4GB 1600 MHz
PSU Seasonic (OEM) Energy Knight SS-500ET 500W
VGA GF8800GT or R6870

The only thing I did before it died is turned off PSU, shorted two pins to reset CMOS for few seconds, turned on PSU, shorted power switch pins. Nothing else. All this time it sat on a cardboard box that came with a graphics card.

I tested the PSU in my old build with Q6600, it worked just fine. I use same PSU in my old build, so I can't test different type/brand PSU at this moment. I RMA Corsair HX650 earlier and still waiting for replacement, so all I have currently are two Seasonic OEMs 500W, and they both work fine in old system.
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a c 122 B Homebuilt system
a c 156 V Motherboard
May 22, 2011 12:48:29 PM

You have much better than average PSU's. At full load, a 6870 needs about 15 amps. So your 500 watt PSU's will power your system.
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May 22, 2011 1:23:18 PM

Yes. So it's either dead CPU or motherboard. That is what I suspected. I bought this Gigabyte motherboard because I wanted to test the CPU as my Asus P7P67 Pro and HX650 died (melted 12v 4pin connector).

I'm really "lucky", with second motherboard and still don't know whether I should RMA my CPU or not.
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May 31, 2011 9:17:54 AM

Tried another processor in it and it worked. So it looks like my processor is dead :( 
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November 2, 2012 4:14:04 AM

Hello

I wanted to add my experience. This thread helped me

I have Asus p8z77 I delux mobo. PUt in my old i5 2600K

I had fans power up. No display. and NO post. mobo led was green (ok)

at first the system would start.. for about 10secs without post.. turn off and restart its self and stay powered up.

I played with upgrading the bios, reset cmos, everything. Still could not get any beeps or a display

It turned out to be a bad CPU.
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