One memory slot causes memory errors on whatever RAM module installed
Actually My iMac is Late 2015 27” i5 3.3GHz for some reason it wasn’t in the list.
Close to the purchase early 2016, I ordered and installed 2 8GB RAM modules from OWC, in addition to the two 8GB modules (from Crucial) that came with the iMac. they all worked fine until recently.
In the last months I experienced dramatic increase in app crashes, daemon crashes, and strange log lines, until some software developer (Mike Bombich from CCC) whose daemon crashed on me, and I sent logs to - suggested that maybe I had a bad RAM module.
I ran Apple diagnostics - which passed OK. I then downloaded a famous memory testing tool called MemTest86 v8.4 - which boots from a USB, and performs long and thorough memory tests. It ran for about 9 hours - and reported thousands of Memory problems. Of course I was sure there was a bad RAM module.
Since I have lifetime warranty on OWC modules, I pulled out the Apple original modules, and ran the tests again with only OWC modules installed. Tests passed without errors. I then replaced them with the originals - and tested again, this time with only Apple-provided Crucial modules. Again - no errors.
I got puzzled. I cleaned the ram seat, re-seated and re-ordered the 4 modules and tested again - Errors returned.
I remembered that both OWC and Crucial modules worked fine when installed in slots 1 and 3. So I pulled just one module out of slot 0 - and now ran the tests with 3 modules (24GB) at slots 1,2,3 — Still thousands of errors. Tested again with slots 0,1,3 — and got no errors.
VERY-LONG story short (each test takes 6-9 hours) - All RAM modules perform perfectly - unless they’re seated in slot 2 - which I suspect is faulty. I reseated the modules so many times now, I’m quite sure there’s no dust or some corrosion there.
My question: What else can be done here? Is anything there “fixable” is it reasonable to give up 8GB and live with just 3 modules? Should I invest in 2 16GB modules instead?
Any advise will be greatly appreciated.
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