Need someone who knows something about mobo circuitry pls

[zigzag03]

I have an Asrock z87m Extreme4 with an i5-4670, which has been working fine. After moving it around to a different case, I've begun to get the following message on boot: "CPU cannot recognize the memory in Channel A. Reseat or replace" or something very close to that. All the ram I've tried are on the list of approved memory, and of course, was working fine for quite some time. It doesn't matter which A chan slot I use, it only recognizes the B chan memory. Have swapped around all the permutations, have populated all 4 slots and it reads and reports all the B chan memory. Have updated BIOS, altho I'm having trouble getting to see and flash the very latest, but have come up at least one level from what was there before.
So my problem is not the memory, and I've been assuming must be mobo. But it seems unlikely to be a bad physical slot issue, unlikely that both failed physically, so I guess my question is, is there a common point downstream from the memory that would fail and take out both slots, or could it be the cpu itself? Cpu seems to work fine otherwise, all cores reporting etc. What say you guys who know something about how a mobo is "wired"?

 

[crashtech]

Did you remove the CPU for any reason?

 

[Squeetard]

Remove from case and test. You may be touching on the bottom somewhere with a short.

 

[zigzag03]

yes I did remove and reinstall the cpu, and I'll revisit that and look to my mounting points, thank you

 

[zigzag03]

I thought I started this thread in the Mobo forum, now I find it in the cpu forum, typical for the way my day is going...

 

[crashtech]

if the CPU has been removed, remove it once more and carefully inspect the pins in the socket for damage. Strong light, a magnifying glass, and patience definitely help. It's extremely common for a pin or pins to become damaged accidentally, and many of the pins are for the memory controller onboard the CPU.

 

[zigzag03]

i will inspect it closely, thank you.

 

[Tuna-Fish]

yes I did remove and reinstall the cpu, and I'll revisit that and look to my mounting points, thank you

+1 from here for looking into the cpu socket -- this sounds exactly like a bent/snapped pin in the socket. If bent, you can possibly bend it back by getting a mechanical pencil, fitting the pin in the tip of the pencil and really slowly bending the pin straight. If it's snapped and you can find it, or you snap it bending it, I've heard of a guy who successfully fixed theirs by taking it to a goldsmith and having them solder it back with gold.

One thing to look out is that even if all pins are fine, having some kind of conductive trash (liquid droplet maybe?) among them might cause same error.

 

[andy2000]

Sometimes all it takes i reseating the CPU. Also, finger prints, dust, or heat sink compound on the contacts can cause problems. It's not a bad idea to clean the bottom of the CPU with alcohol if it may have been touched. Inspect and blow out the socket with compressed air.

 

[zigzag03]

guys you were absolutely correct, once i pulled the chip back out the bent pins are obvious. I can't believe I was so careless. I don't have what it takes vision or magnification wise to deal with it, but there's a little shop down the street that specialized in jewelry repair that I'm going to take it to and see if they have what it takes to straighten them. Thanks again to all for your input. zz03