Memory test failed, cpu, mb or ram?

[KNP54]

Hello all,

I have a stability problem with my rig and I did a memory test with each stick individually using Passmark MemTest86 v7.1 (free).

One of the sticks fails the test, but only when all cores are running in parallel, sometimes only on core 7, or core 4 and looking at the results it seems to affect a narrow range of memory address and only 1 bit on the data bus.

But, if i redo the test with a single core (tried core 0, 4 and 7), the stick passes all the test.

So is the ram stick defective, or is it the MB, the CPU?

Here are my specs:

Intel Core i7-4960X @ 3.6GHz
Asus Rampage IV Gene
G.Skill 4x8GB F3-1866C8Q-32GTX @ 1866MHz
EVGA Geforce GTX Titan Black
Corsair H100i AIO water cooler
Corsair AX860i power supply
500GB Samsung 840 EVO SSD
Seagate 4TB HDD
Oculus Rift VR Headset

[GSKILL TECH]

All the other modules pass except that one?

[KNP54]

Yes.. All other modules pass the tests.
Only 1 module fails the test and only when doing the test using all cores in parallel.

[GSKILL TECH]

Send it in for RMA:

http://www.gskill.com/en/rma