If you’ve been around computer geeks for a while, you may have heard the phrase “it refuses to POST” or “it made it to POST” or any other variation. But what exactly is POSTing on a computer?
What Does POST Mean For PCs?
For PCs, POST means “Power On Self Test” and it is a process that all computers go through when they turn on. When a computer POSTs, it checks that every component it needs is plugged in and working. The computer will turn on after POST or communicate any problems it finds during POST with a series of beeps.
POST is the process your computer goes through when you turn it on, before it actually “turns on” where you can use it.
If you know what the BIOS is in your computer, then POST happens before your computer even goes into the BIOS. It is the initial test of a computer’s components before the computer can be used.
When your computer POSTs, it performs a series of checks to ensure you have a CPU, graphics processor of some kind (integrated / dedicated), that you have RAM, and that nothing is plugged into the wrong port.
POST helps you protect your PC from permanent damage. For example, I once built a PC using a shorted-out component. My computer would not POST, and I couldn’t figure out why.
When I tested the faulty component on a different PC, the component started smoking and almost caught on fire.
So, POST can protect you from damaging the rest of your PC if one of your PC’s most vital components is missing, shorted-out, or faulty.
Often times, when you build a new computer, you may have trouble turning the PC on for the first time. In some cases, your PC may not even POST, meaning you cannot access your PC’s BIOS or operating system.
When your PC does not POST, you may notice its case lights don’t turn on or its fans spin but nothing is displayed.
During POST, your motherboard may make specific beeping sounds if there is some component that is failing the POST sequence.
It’s also common for motherboards to come equipped with LED lights that indicate the status of different systems checked during POST.
If your PC is not POSTing, you may be able to find the problem by looking at these LEDs on your motherboad.
For example, if your hard drive is malfunctioning, then you may notice the LED lit up on your motherboard that indicates the boot drive has failed POST.
What Is The Point Of POSTing A Computer?
POSTing a computer ensures that the computer has all of the necessary components to safely run, that none of the components are damaged, and that they are all working as intended. All computers POST before starting and if a computer fails the POST test, it will not turn on at all until the issue is fixed.
POSTing keeps our computers safe and sound. It makes sure that silly mistakes like our computers don’t start with the hard drive plugged into the wrong spot, which would probably lead to a fried motherboard.
POST stands for “Power On Self Test”. So, it’s pretty much just a quick test that runs through every component in your computer and makes sure that they’re all working properly.
It makes sure, for example, that you have a CPU and that it works. If your computer fails the POST test, then it just won’t turn on.
So the point of POSTing is to ensure that everything in your computer is on the up and up before it starts.
How To POST A Computer?
To POST a computer, simply turn the computer on. When computers are turned on, they automatically POST before entering the Operating System. If your computer successfully POSTs, your motherboard will likely beep once. If POST fails, then your motherboard may make a series of beeps depending on the error.
Your computer will immediately POST when you press the power button, however, the trick is to learn what your computer is telling you when it POSTs.
When a computer POSTs, it will run a bunch of tests on your computer, and then it will send out a code via beeps.
People that build computers often learn how to “read” these beeps, so they can tell if their computer is starting properly, and if it’s not then they can read what the issue is.
For example, a computer that doesn’t POST and refuses to start, may beep 3 times in rapid succession. This may mean something like “hey you have no CPU plugged in” or “hey your fan is messed up”.
What the beeps mean, exactly, will depend on what BIOS is installed on the motherboard.
In addition to beeps, modern motherboards sometimes have LED lights that indicate the status of each systems check during POST.
For example, there is typically an LED that indicates the status of your boot drive, and one that indicates the status of your CPU fans.
Where On A PC Is The POST?
The POST takes place on the motherboard of a PC. POST is a test that every PC runs before start up. The test tests every vital component inside of the computer from the CPU to the Keyboard controller. The motherboard POSTs the computer, but the exact POST method is determined by the BIOS that is installed.
The POST happens on the motherboard, but it checks pretty much everything that is plugged into your PC. Your CPU, your RAM, your boot drive, and your cooling system are all checked during POST.
The POST will always happen on your motherboard when you start your computer, but exactly what is tested, how it is tested, and in what order it is tested will depend on the BIOS installed on your motherboard (not the motherboard itself).
Two of the same model of motherboards may have different BIOS, which have different POST methods.
What Is No POST For PCs?
A no POST means that the computer did not pass the POST test initialized by its motherboard on startup. When a PC starts, a POST (Power On Self Test) is run that checks every component in the computer for problems. If there are no problems, the computer starts up, otherwise the computer “doesn’t POST”.
No POST and “refusing to post” is just terminology for when a computer fails to POST on startup. All it means is that something is wrong with one or more of the components inside of the computer.
If you turn your computer on and it doesn’t start, but you hear a few beeps or one long continuous beep, then it’s probably because your computer is refusing to POST.
If you know which BIOS is installed on your computer, then you can figure out what the exact problem is by listening to the beeps.
People that build computers are very good at reading beeps and determining why computers are refusing to POST.
Since POSTing happens before data is even sent to the monitor, PC builders can’t rely on visual aids for determining what is wrong with the computer.
This means POSTing is the only method available for troubleshooting a stubborn computer that refuses to boot.
Why Do Computers POST
Computers POST in order to determine if there are any problems with the components inside of the computer before the computer actually starts and loads the Operating System. This prevents the Operating System from starting when something is plugged in wrong, damaged, or faulty, which may cause permanent damage.
Without POST, we’d pretty much be crossing our fingers every time our computers turned on. For example, if you have something seriously wrong with your CPU, then you don’t want Windows to start.
If Windows did start and run some operations using your CPU, it could damage even more components in your computer.
POSTing just makes sure that all of your components are working as they should and that your computer can start up safely.
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