Bad RAM looks like a software problem for weeks. Apps crash, Windows throws a memory-management BSOD, games hitch, and someone sells you an “upgrade.” Sometimes you do need more capacity. Sometimes one stick is half-dead and adding a second just gives the board more ways to crash. I’ve bought the upgrade first. Don’t.
Run a real test, not Task Manager
- Windows Memory Diagnostic is acceptable as a first pass. It is not complete.
- MemTest86 from a USB stick overnight is the actual test. One pass is not enough; four is a start.
- Test sticks one at a time. A kit of two can hide a single bad DIMM.
Reseat before you replace. Dust in the slot and a stick that didn’t click on both ends cause the same errors. On laptops the SODIMM often looks seated and isn’t. Push until both ends catch.
If a stick fails
Match what the board already likes: DDR generation, SODIMM vs DIMM, speed the rest of the kit runs. Mixing sizes works on a lot of machines and causes weirdness on others. If I’m replacing, I buy a matched kit and keep the survivor as a spare.
On the bench
Matched SODIMM or DIMM kit (only after a failed test)
Don’t buy RAM because a thumbnail said 16GB is the new 8GB. Buy it because MemTest failed, or because you actually fill what you’ve got. Check the service manual for the generation. DDR4 and DDR5 are not interchangeable. I still see people mix that up.
- Confirm SODIMM (laptop) vs UDIMM (desktop).
- If the machine is DDR3, stop browsing DDR4 listings.
Verdict
Reseat, test overnight, replace the stick that failed. More capacity is a different conversation, and it comes after the current memory is proven good.