Shopping Used CPUs
Brand new, it’s extremely rare for a CPU to have an issue given how small and incredibly complex they are - if there’s a manufacturing issue it’ll almost always be discovered long before it reaches the end of the production line.
As such, CPUs tend to be the most resilient used part, lasting well over ten years when run within their factory specifications. Often even longer - most of the CPUs from the 80s and 90s still run fine years after the rest
of the system burnt out!
Of course, there are still some things to watch out for.
This is an easy one. Any CPU with broken-off pins is to be avoided. If a single pin or two can’t make a connection the chip may boot and even test fine, but long-term stability won’t be guaranteed. In a best-case scenario you may
experience sporadic freezes and lockups, but in a worst-case you risk further damage to the processor or motherboard.
It’s also possible that pins could be bent. Even if the pins are straight in pictures, shipping damage could occur. If you’re comfortable working with a straight edge of some sort, straightening the pins is an option you can consider before trying to return the damaged part to the seller. Try contacting the seller before you attempt this though, as some larger second-hand outlets may prefer an exchange from the get-go.
Damaged Capacitors or Resistors
This one is a little more difficult to spot. On the underside of the CPU, usually in the middle of the pin or land-grid array, there are typically dozens of tiny capacitors and resistors that regulate the flow of electricity inside
the CPU die. These protrude from the PCB on land-grid array style CPUs, and are thus more likely to be damaged from mishandling.
Because of their size, it’s easy to miss a broken-off capacitor with a passing glance, and much like bent pins they could be damaged in transit. Take a close look at the CPU’s underside and check for any flat or rough spots where a capacitor could be, or better yet, find an image of your model and compare. A broken-off transistor does not necessarily mean the CPU won’t work, but certain operations or overclocking could cause crashes or instability that an undamaged CPU wouldn’t exhibit. It’s also entirely possible that it could damage your motherboard or other components in your PC.
In any case, damage like this can’t be repaired. We don’t recommend using CPUs with capacitor or resistor damage even if the seller claims it tests fine.
Though we’ve seen that CPUs have the lowest failure rate of any component, it’s worth mentioning that we consider a working CPU as one that can run at its stock clocks without issue under adequate cooling. Shopping used CPUs
for their overclocking performance introduces more unknowns - you’re now adding the silicon lottery and the prior owner’s overclocking expertise into the equation, as well as motherboard quality.
The idea that silicon degrades is dubious, but the general rule that excessive heat is bad for any electronic component still applies. Anyone who ran a chip overclocked should have used a solid cooling solution (such as an all-in-one cooler or a custom water loop) and can attest to the frequencies and voltage used, as well as temperatures under load. If they can’t provide this information then look elsewhere, especially on popular overclockers like the i7-2600K or AMD FX-8000 series.