psuThis is an instance which has caused many a PC builder some serious frustration – only because they didn’t know the root cause of the problem.

Situation: You upgrade a component of your PC, be it the processor, graphics card or what-have-you.

After the upgrade, you start getting random BSODs and you have absolutely no idea why. You think it might be the new component you installed, but that checks out fine and nothing else appears to be exhibiting any problems.

At this point you decide to test your RAM using Memtest86, and wouldn’t you know it, you get memory errors, so you’re convinced one of the RAM sticks is bad.

Like a good PC builder, you test each RAM stick individually (as in take out all but one stick of RAM and test each with Memtest86). To your surprise, all sticks pass the test. The RAM is not bad. This makes you happy, but confused.

After that you place all the sticks on the motherboard and run Memtest86 again, and it reports memory error again.

imageAt this point you test each RAM stick and slot individually. Any RAM stick on its own in any RAM slot passes the memory tests, proving once and for all that none of the RAM you have is bad.

Once again, you place all the sticks in the motherboard, run Memtest86 again, and again it says some of the RAM is bad.

What’s going on here?

What’s going on is that the RAM isn’t bad, it’s probably your power supply. More specifically, the PSU isn’t providing enough power to run all the stuff in your computer.

That new component you added in be it an upgraded CPU, graphics card or anything that draws more power is drawing just enough to go beyond what the PSU can handle, and this is why you will encounter BSODs completely at random. Whenever the draw gets too high, the RAM momentarily doesn’t have enough power to be accessed and Windows (or Linux for that matter) chokes because it’s trying to get to an address that isn’t accessible.

The reason all the RAM sticks pass the tests individually but not all together at once is because one stick doesn’t use as much power draw, therefore one stick will always pass the memory tests. If you have 4 sticks for example, having 2 or 3 installed will probably pass, but when all 4 are installed, nope. Too much power draw for the PSU.

The end result is that because of a not-good-enough PSU, you were getting false-positives for bad RAM.

Workarounds until you get a better PSU

You still have to use your computer until you get the new PSU, and these workarounds will usually limp along your PC until it arrives.

Unplugging USB charging devices you can go without temporarily

USB devices like Flash drives don’t draw that much power, but if using your PC to charge something via USB, try to avoid doing that until you get a new PSU installed.

Purposely running less RAM

This is the easiest option. All you have to do is remove one stick of RAM and set it aside until the new PSU is installed. All that’s usually required is the removal of one stick. For example, if you have four 1GB sticks for 4GB of RAM, remove a stick and run 3GB.

What watt rating should you go with for your next PSU?

The maximum power watt rating absolutely should not dictate which PSU you buy, for the reason that just because PSU’s specs states it outputs a specific amount of maximum watts doesn’t mean it can actually do it.

Cheap PSUs usually cannot deliver over 350 watts no matter what the specs state as its maximum power – even for ones rated at 500 watts.

The general rule of thumb is to not buy cheap PSUs. It’s par for the course that you’ll have to pony up at least 40 bucks at bare minimum just to have a PSU that can do what the specs state it can.