How can I be sure CPU is dead and not motherboard?

[Engr62]

The other day, I purchased a 27-in. monitor for my son's computer (i5-2500K at stock on a z77 motherboard). It has only HDMI & DisplayPort connections. I previously had a 21.5-in. monitor with DVI port connected to his computer, and he used the HDMI port on the monitor to connect his PS4. His graphics card had only DVI, HDMI, and VGA connections.

In order to allow him to still connect his PS4 to the monitor, I replaced his graphics card (HD4850) with one I had in another system (HD7770) that has DVI, HDMI, and 2x mini DisplayPort connections.

When I tried to boot his system, it gave 5 short beeps and stayed stuck at the motherboard logo (ASRock)--it wouldn't continue to boot. I turned the power off, then rebooted. The system came up the second time; however, I couldn't change the resolution from 640x480. I did some searching and discovered that many DisplayPort cables are not within spec--Pin 20 has some voltage (~3V) instead of 0V per the spec. So, I connected the monitor via HDMI instead until I could get a better DisplayPort cable. The system seemed to run fine through the HDMI connection.

Tonight I tried to boot up his system when the new DisplayPort arrived. His system now gives the 5 short beeps and won't boot. I read online that the 5 short beeps indicates a CPU failure. One troubleshooting tip I read said to remove the RAM, power on the system, turn it off, replace the RAM, and power on again. That process allowed the system to boot, however locked up within a couple of minutes in Windows. Upon powering the system off and turning it back on, it's back to the 5 short beeps.

My question is:

Can I be sure that the 5 beeps really indicates a CPU failure, or could some kind of motherboard failure give the indication of a CPU failure? It will be bad enough to replace the CPU, but z77 motherboards are fairly expensive. I hate to spend money on a CPU only to find out it was the motherboard though.

I don't have access to anyone or a local shop that has a 1155 motherboard to mount the i5-2500K in to be sure it is the culprit.

 

[UsandThem]

Really the only way to determine if it's the CPU or the motherboard is what you said you can't do; Put in another CPU and see if boots, and if it doesn't, it's a board issue. You can buy another CPU, but like you said if it's not the issue, then you are buying a board. Have you tried different ram in it just in case?

You are in the same place I was in a few months ago. I had a good i7-3770k and a flaky z77 motherboard. Instead of (at the time anyways) paying $200 for one of few new z77 motherboards left, I just bit the bullet and jumped up to a z97/Haswell CPU.
I can sell the 3770k to offset the unexpected platform change.

LGA 1155 is long dead. You can still build with it, but you will pay. Probably not the answer you wanted to hear.

 

[AnonymouseUser]

Remove the HD 7770, clear CMOS, and boot using the onboard video. See if that gives any problems.

 

[UsandThem]

Yeah, I agree with the above as well.

It was late when I read your post, so I kinda skimmed over it half asleep (stupid insomnia). I didn't realize it was working until you added a new card. Hopefully clearing the CMOS will get you up and running.

It would be very odd what you did would kill a CPU.

 

[Engr62]

AnonymouseUser & UsandThem:

Thank you for your suggestions.

I have a CORSAIR CX series CX430 430W in the system.

I removed the video card, reset the CMOS (by removing the battery for 15 seconds), then connected the monitor to the on-chip video from the i5-2500K. The system now boots without the 5 beeps. I tried to re-install the HD7770--same thing--5 beeps and no boot. I then repeated the process (removing the video card, clearing the CMOS, and booting with the monitor connected to the on-chip video)--then re-installed his old HD4850. Same result, 5 beeps and no boot.

I'm now running it off of the on-chip video. It boots up fine, but It locked up after it was on for a while without use (perhaps some power management issue). I rebooted it, and ran chrome browser, MS Word, and MS Excel on it, and it seemed to run fine. I'll leave on for a while without using it to see if it locks up again.

So, does it sound like I have a power supply problem instead of a CPU failure?

Thanks for your input.

 

[AnonymouseUser]

It's definitely possible the PSU is the problem, but 430W should be enough for the HD 7770, so I don't know why it caused any problems.

Maybe there is a problem with that PCIe slot, so if your motherboard has a second PCIe slot you could try installing the GPU there and see how that works.

 

[UsandThem]

While the size of the power supply is fine, you didn't say how old it is.

Maybe it is on its way out. If you have another power supply to test, you could rule that out.

If you have the same issues with another power supply, it will likely be the motherboard being the problem, and like AnonymouseUser stated, the issue might be with that particular PCI-E slot.

 

[Engr62]

Thanks for the help in troubleshooting this problem.

I tried both video cards in another PCIe slot. Same results with each... 5 beeps and no boot. The system seems to run OK when using only the on-chip graphics. But that's not an ideal situation if he wants to do any gaming (although he primarily will game on his PS4).

The power supply was purchase from Newegg in 2014 but wasn't used until we put this system together about 1 year ago.

If the PS is bad, and the extra load on it from the video card is taking away some of the juice from it--not leaving enough for the CPU--would that cause a CPU failure beep code?

 

[AnonymouseUser]

Yes. If the PSU is bad for whatever reason and cannot supply enough power to the CPU when the GPU is installed then the motherboard won't recognize the CPU. It sounds odd that the PSU could have been damaged by the HD 7770 because it uses less power than the HD 4850, but with PCs I guess anything is possible.

I would double-check all motherboard connections and make sure they are properly installed, especially the 4- or 8-pin CPU 12v power connector and the 24-pin motherboard connector. If the connections are fine then try another PSU.