Tips & Tricks for Shopping Used PC Parts

by turbolence1988MAR 24TH, 2019

Shopping Used Memory, Drives, and More

We’ve touched upon the issues to look for with the major components so far, but there are still some areas left to look at. Here’s how the rest of the rest stack up when you shop used.

RAM: Bad Memory Addresses

Buying used RAM is usually safe - a faulty memory stick will usually cause a failure to POST before it can even be tested. It’s still possible for some memory errors to occur only after the system has written to a bad memory address, which will result in a crash. Knowledgeable sellers may provide results from Memtest86 or similar memory testing applications, but we still recommend doing at least one full pass yourself after purchase to verify their integrity. Memtest86 is designed to detect errors as quick as possible, so if a stick is faulty it’s likely the test will throw an error after only a few minutes of runtime.

Bryan at Tech YES City indicates that any memory stick that throws errors in a memory test is completely irreparable, and we recommend returning the defective stick for refund ASAP.

SSDs: Bytes Written

Despite their reputation for speed and reliability, SSDs will wear down over time. Much like an SD card, the NAND cells that make up the drive’s memory will only tolerate a certain number of erasures before they become unusable, effectively bricking the drive. These are typically represented by manufacturers as MTBF hours, or Mean Time Between Failures, calculated using assumptions about typical user habits.

The metric we’re most concerned with on a used SSD is the total amount of data written to the disk over its life*. Most SSDs automatically record this value and store the total amount of host writes in their S.M.A.R.T. attributes, visible using programs like CrystalDiskInfo. Some brands are more durable than others, but in general, a used SSD can tolerate about 100 times its rated capacity in writes before its lifespan becomes questionable. This means a 500GB SSD should be good for up to 50 TB in writes, and if the drive is nearing this mark then it wouldn’t be the best choice for an operating system or any disk where data loss would be catastrophic. Much like RAM, motivated sellers may provide this information upfront, but it’s worth checking yourself once you have it in your hands regardless.

*Ideally we would want to know how many bytes were erased from the disk, as this is what wears down NAND, but this information isn’t available on most drives. We have to assume a write requires an erasure of at least equal size first.

HDDs: Power on Time, Bad Sectors

Similar to SSDs, hard drives also utilize S.M.A.R.T. metrics that can determine their life expectancy. In this case, we’re looking at Power-On Hours (POH) and seeing how close the drive is to the typical 5 year (43,800 hours) life expectancy as a basic indicator of drive health. Total writes and reads are less important here. Three years (about 26,000 hours) of POH is about the upper limit you’d want to consider, and at this age the discount over a new drive should be significant.

Another attribute to check for is whether any bad or reallocated sectors have been reported by the disk. A couple reallocated sectors are no major cause for concern; the drive’s firmware detected a bad sector before it was used and remapped it to a good one reserved for such an instance. However, a bad sector that is not recoverable means unexpected data loss has occurred, and the drive should be considered defective as further bad sectors are likely to follow. Again, sellers may or may not show this data and it’s worth running a quick check either way once you receive the drive.

CPU Coolers: Replaceable Parts

This is more of a reminder than anything else, but remember that the fan on most aftermarket air coolers can be replaced. A noisy or dead fan can be swapped for one of equal size, and if it uses a standard PWM fan like the ones you find on Noctua or Cooler Master products you can repurpose a case fan as needed.

All-in-one liquid coolers can also have their fans replaced, if a bad fan is indeed the problem. AIO failures are typically either leakage somewhere along the tubing (typically at the ends where a fitting would be on a water loop), or a failing pump. Neither of these issues are easily fixed as AIOs are intended to be closed-loop systems that can’t be serviced. We recommend buying these used only with utmost caution.

Power Supplies: Not Recommended Used

The only part of the computer more critical than the motherboard is the device that feeds all of the electricity into the system. A power supply needs to be robust, reliable, and in perfect working order at all times lest it decides to send itself up in a puff of smoke, taking any number of components with it in the resulting shock to the system. Thus, while you can buy used power supplies, we don’t recommend that you do.

This is the one area where it pays to go new. Good quality 80-Plus rated PSUs can be had for under 30 dollars on the regular, and though they may not put out incredible amounts of power nor be modular, they’ll be much more reliable than any used supply. Additionally, some manufacturers will have their warranty cover not just a blown PSU but all the other components of your system affected by its failure as well. All told, we just can’t in good conscience recommend taking the chance on a used PSU.