"New" CPU degrading rapidly?

lexidobe · May 22, 2025

Long story short, I bought what was listed as a "100% new" tray i7-6950X to upgrade my main rig's i7-6850K. What I received was a CPU that appears to be in good condition and was cleaned up well and may appear new to an untrained eye, but has definitely been installed before since there's marks from socket pins on the pads and thermal paste in the hole on the IHS. I immediately contacted the seller, who was quick to say that the residue and marks was just from them testing it before shipping and not from use, which I can't think of a way to prove or disprove. Here's the listing if anyone is curious https://www.aliexpress.us/item/3256807490736954.html?spm=a2g0o.productlist.main.1.3f709zue9zue8I&algo_pvid=0add411b-d540-4457-a50d-246f708fe85f&algo_exp_id=0add411b-d540-4457-a50d-246f708fe85f-0&pdp_ext_f={"order"%3A"2"%2C"eval"%3A"1"}&pdp_npi=4%40dis!USD!218.44!218.44!!!1563.66!1563.66!%40210337bc17479331808435976e1636!12000041770821832!sea!US!6292277706!X&curPageLogUid=4K3kuq9DgItf&utparam-url=scene%3Asearch|query_from%3A

I was about to send it back since I paid a significant premium for a new CPU, but with a 3 month return policy, I decided to give it a chance and was initially impressed when I was able to get a stable 85 mV core undervolt. From experience with 3 other Broadwell-E CPUs, it seems like the average stock core and cache voltage headroom on Broadwell-E was roughly 75 mV +/- 5 mV. The cache was never stable with more than about a 60 mV undervolt, which seems to have remained constant.

However, over the last 2 months, I have had to gradually reduce my core undervolt to now just 64 mV to maintain stability and the initially stable 85 mV core undervolt now instantly crashes. At this rate (~10 mV degradation per month), after less than a year of use, it won't even be stable at stock settings anymore!

For reference, the i7-6850K that I bought new in 2016 has been running 24/7 until 2 months ago ran at the same 74 mV and 76 mV undervolt on the core and cache respectively its whole life (an extra 2 mV on each for stability) and I never once had any stability problems or had to make adjustments. That CPU also spent years running at 100% running FAH, doing long renders, gaming, Prime95, Aida64, etc and I could still be convinced that it's new since it's shown zero signs of degradation, which I can confirm as the original owner.

Aside for a couple hours of overclocking testing in the first couple days never exceeding 1.3V core, 1.85V input, or 75 degrees C and no heavy loads while overclocked other than a handful of Cinebench runs. It's cooled by a custom loop and never exceeds 40-45 degrees C stock, so nothing I did should have degraded this CPU.

The other odd difference is the i7-6850K seems to "soft" crash when pushed slightly too far for the voltage and would tend to blue screen, crash the program, etc and would always restart gracefully with the reset button while this.... thing goes from seemingly totally stable to hard crashing to the point of the power and reset buttons being unresponsive once it decides again it wants another mV of core voltage (which has happened quite a few times), often forcing me to shut off the PSU. Not sure what that means (if anything) but that's another difference I've noticed.

Any ideas of what could be going on? Maybe it had a hard life before I got it and the degradation is just now starting to become more exponential? Maybe it was actually new and defective and degrading rapidly? Either way, I'm thinking it may be time to send it back and either insist on a full refund or an untested verifiably new replacement because I don't want to get stuck with a defective CPU. I have never experienced any measurable CPU degradation like this before (although I run everything very cool, don't overclock long term, and never set high voltages), so any input or suggestions would be greatly appreciated!

CPU: Questionable i7-6950X (previously rock solid i7-6850K)

GPU: Titan V

Motherboard: Asus X99E-WS

Cooling: Custom loop

RAM: 64GB G Skill Trident Z RGB 3200 MHz (only running at the 2400 MHz the CPU is rated for)

PSU: Seasonic Prime Ultra Titanium 1000W

Case: Fractal Design Define R5