Half Ram, PCI-E slots missing--Need CPU to test mobo

Axman

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A little background. I have an older desktop that's had its first hiccup in about five years. I just bought a new laptop so it will be a couple of months before I can build a new desktop and I'd rather just get it, old as it is, back up and running in the meanwhile.

A couple days ago I turned on my desktop and got nothing but beeps. I looked up the error code and it was "unrecognized GPU." Seeing how all of the parts to this point were recognized and working fine, I assumed that the power supply wasn't powering the GPU.

Switch PSU, same error. Move GPU to other slot...works fine. OK, weird, messes up air flow, but whatever, it works.

Start it up, boot, get into Windows, and my RAM disk isn't running. I'm running 32 gigs of ram, 12 for system, 20 for RAM disk (page file, ReadyBoost, browser caches -- try it, it's part of the reason I'm able to run an older PC).

That's when I notice I only have 16 gigs of ram working.

Reboot, check UEFI, says only two of four sticks are there. This is where things get weirder.

I did a little testing and all four sticks run fine. All four slots work, too. If I put RAM in slots A1 and B1, I get 16 gigs dual-channel. If I put RAM in slots A2 and B2, I get 16 gigs in dual channel.

If I put in all four sticks, A1 and B1 disappear in the UEFI and only A2 and B2 work in dual-channel mode with 16 gigs.

If I put in two sticks in the same channel, A1 and A2, only slot A2 works in single-channel mode with 8 gigs. Same for B.

When I have all four sticks installed, in the system browser, the UEFI shows all four slots populated. But they're not there in any of the other settings.

And in Windows, CPU-Z shows all four sticks of RAM installed with 32 gigs to play with.

https://imgur.com/a/U63gAtN

All of this leads me to believe it's the CPU, not the motherboard. The RAM tests fine. My only concern is that the second PCIe slot also shut down but that's also part of the CPU interface IIRC.

Also another reason I suspect the CPU is that it only unlocks to x38 -- it should unlock to x42.

Currently the computer has an I5-3750, an LGA1155 CPU. The mobo is an Asrock Z77 Extreme 4, the RAM is 4x8 gigs G.SKILL TridentX DDR3 2400.

Anyone else ever run into a burned out IMC with their older Ivy Bridge chips?

I could test the CPU if I had an extra LGA1155 processor lying around, but I don't. I will pay to borrow (I'll return it after testing) someone's known good LGA1155 processor if you have a spare. Twenty bucks and I'll cover shipping? If you're in or near Denver I'll drive and get it back to you in the amount of time it takes to test my theory.
 
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Axman

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Went ahead and bought a processor with a solid return policy. I'm still 75% sure it's the CPU. We'll find out in a few days.
 

Araxie

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Feb 11, 2013
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Agree with CPU broken IMC and probably direct PCI-E Lanes.. a cousing of mine had similar issue with an older 3570K and turned to be the CPU.. his GPU worked in secon slot because the mobo had PLX chip for more PCI-E Lanes maybe your GPU it's also working on PCI-E lanes from mobo and not the ones that go straight to CPU.
 

vick1000

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Sep 15, 2007
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Could be socket corrosion too. If it was stored in a humid environment. Some Deoxit 5 aresol might fix it.
 

Axman

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I will absolutely try this. Because the system exhibits the same behavior with the replacement CPU. It's strange because there's no outward signs of damage, anywhere, no blown caps, no traces of magic smoke, nothing.
 
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