So you finally put together the PC of your dreams. It’s all done. You plug it in, hit the Power button and… it doesn’t power on. Your PC didn’t POST. Here’s what to do.
What Is POST?
The term POST stands for “power-on self-test.” It’s basically a series of tests that your PC does when you power it on. The POST process ensures all of your hardware is properly connected and working correctly before loading your operating system.
Those few seconds that pass between the moment you hit the Power button and the moment your BIOS splash screen shows up on your monitor? That’s a POST. If the POST finds all the hardware your PC needs is present and in working order, your PC will continue the boot-up process and load up the OS. If, however, it detects something wrong, it’ll shut back off immediately.
A POST can fail for multiple reasons. On older computers, it can indicate an essential piece of hardware has died. If it’s a completely new PC, though, more often than not, it’s user error — you probably forgot or messed up something while building it. Here are a few things you can try.
Remove/Reseat the RAM
One reason why your PC might not be booting up is because of the RAM. It’s possible that you didn’t install the sticks correctly, or that you didn’t push them all the way into the slots.
Remember that when installing RAM, you need to make sure the small indentation in the stick is aligned with the corresponding barrier in the slot, and you also need to press down the small tabs at the end of each stick. Then, you just press the stick down until the tabs go back up themselves. You might need to give it a little bit of force — they can be really hard to press down.
If you’re 100% sure they’re properly installed, though, you should rule out a hardware issue. To troubleshoot it, you should remove one of the sticks, then try starting up the PC again. If it boots up with just one, you might need to replace your RAM. If you tried both sticks individually and they both work, the issue might be something else.
Check/Reconnect the Power Supply
It might sound silly, but sometimes your problem is just related to the power supply being improperly connected. It might not even be doing a POST at all.
Check if the power supply is switched on, and if it is, make sure that all cables are connected to all components. Your motherboard should be using a 20-pin connector, your CPU should have its 8-pin connector, and if you have a graphics card, it also needs its PCIe power connector plugged into it. Also, if you have any hard drives or non-m.2 SSDs, they also need a SATA power cable coming from the power supply.
Update Your BIOS
One reason why a POST might fail is that it’s detecting the CPU is incompatible with the motherboard. If you bought an older motherboard and you’re putting a newer chip in it, and the socket is a match, it might still fail because the motherboard’s BIOS needs to be updated in order to properly use the new chip.
Some motherboards have a “flashback” option that will let you update the BIOS by putting the new BIOS in a thumb drive, plugging it into a designated USB port, and hitting a button. In some others, especially cheaper ones, this might not be an option.
Unfortunately, in this case, you’ll either need to return the motherboard and buy a newer one or update the BIOS by actually putting a compatible chip on it. If you suspect this might happen, it’s good practice to purchase a budget chip that came out at the same time as the motherboard, like an AMD Athlon or an Intel Celeron/Pentium, so you can use it to update the BIOS before using the chip you actually want to use.
Remove Peripherals and Add-On Cards
One issue at play could be that there’s one damaged peripheral or add-on card that’s messing up the boot process. In order to try this, you should disconnect your keyboard, your mouse, and all peripherals you might have, then boot up. If it turns on, one of your peripherals is causing trouble. To troubleshoot that, turn the PC back off, connect one of them, and see if it turns on, then repeat the process until you’ve found the culprit.
What about add-on cards? The one add-on card most people have is the graphics card, and if you suspect it, there are a couple of ways you can try it. If your CPU has integrated graphics, you can take out the graphics card and just try turning it on again.
If you don’t have integrated graphics, though, you can try making sure the graphics card is properly connected to the PCIe slot you’re using (and powered by the power supply). You can also try connecting it to another system. If it’s the graphics card that’s causing issues, you’ll want to get it replaced.
Remove and Reinstall the CPU/Cooler
Another CPU-related issue at play could be the CPU, but rather than having a BIOS issue, there could be a problem with the CPU itself. When you’re installing it, you need to make sure that you’re lining up the CPU with the socket just right, and that all pins are making contact with all contact pads. Make sure the CPU is being held down securely right before putting the CPU cooler on top of it, and make sure the cooler is connected to the appropriate header for it.
If you messed up the installation, you should check if you broke any pins on the motherboard (if it’s an LGA CPU like an Intel chip or an AMD Ryzen 7000-series or newer), or in the CPU itself (if it’s a PGA chip like an AMD Ryzen 5000 or older). If you did, that could cause problems later on or could be the very thing causing the PC to not POST.
What to Do if It’s Still Not POSTing
Unfortunately, if the above steps didn’t work, it’s very likely you’re not dealing with user issues anymore. It’s likely that a major component, like the motherboard, is to blame. That happens sometimes, though, and it’s not necessarily your fault. It will mean, however, that you’ll need to do more rigorous testing.
Some motherboards, especially higher-end ones, will have LED lights — either individual lights or a digital LED number panel — that will flash after conducting a POST. If it failed, those lights will let you know what’s wrong. They aren’t really standardized, so you should refer to your motherboard’s manual to know what those lights mean exactly.
If your motherboard doesn’t have those lights, you might be able to buy an add-on POST card. These will go in a free PCIe slot in your PC, and will basically double as the LED lights that your motherboard doesn’t have. Again, depending on which card you buy, you can either get a number panel or a set of lights.
If this is not an option, you’ll need external help. In order to nail down the issue at blame, you’ll likely need to take your PC to an expert that’s able to test—and rule out—what’s wrong with your PC, so that they can tell you the best course of action. If you have another working PC with parts released roughly within the same timeframe as the parts you’re using, you could also take a stab at it and test each part individually.
What About Motherboard Beep Codes?
If you don’t know what beep codes are, they’re beeping sounds made by your PC that are meant to announce the result of a POST. If you hear one single “beep” sound, that means the PC has booted up successfully, and the PC will begin loading up the operating system. If you hear a different sound, followed by an immediate shutdown, that’s a beep code indicating something is wrong.
There are different beep codes depending on what exactly went wrong during the POST, making them an extremely useful tool in helping you nail down what’s wrong and correcting it. For example, RAM issues and CPU issues will have their own beep codes, and so will motherboard issues.
If they’re so useful, why haven’t we mentioned them during the whole post? Basically, for the same reason why you haven’t heard PCs beep after booting up for close to a decade — we’ve stopped using them. You can, however, bring back the functionality by buying a device such as this motherboard beeper and hooking it to your PC. Some motherboards will even come with one inside of the box.
If you do have to buy one, we don’t recommend you do this unless it’s literally the only option you have. Like the LED lights some motherboards have, beep codes aren’t standardized, and there’s a chance that your motherboard, not normally supporting beep codes, has no instructions on what they might mean in the manual.