POST stands for Power On Self Test. POST (or P.O.S.T.) is a sequence of system checks performed by computers and other electronic devices upon power-up. The test results may be shown on a screen, sent by flashing LEDs, or stored internally. The POST operation operates at the beginning of the boot sequence on computer systems. If all tests pass, the remainder of the setup procedure will proceed automatically.
What is POST?
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POST or Power On Self Test is a set of checks performed by software immediately after a computer is switched on to ensure if the main components are working as expected.
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Your device will only move to the next instruction if the hardware is working correctly else the BIOS (Basic input-output system) will issue an error message.
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The results of the POST test are shown on the computer screen. The POST function runs at the start of the BOOT function. When the POST process is successfully finished, the process of starting the computer is enabled. Bootstrapping starts the initialization of the OS or the operating system.
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Computers are not the only device that runs a post. Some other devices and appliances such as medical equipment use the same technology.
What is the role of POST?
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POST is the first step on the Boot sequence. POST is going to run whenever you restart your computer even after a minute of shutting down or switching on your computer after a month.
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POST does not depend on any operating system. In fact, a device does not even need to have an operating system installed on the hardware for a POST check to run. The POST run is controlled by the BIOS of the computer system, not any installed hardware.
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The major role of the power-on self-test is to check if the basic devices of the computer are present and if they are in working condition like the keyboard and other hardware devices and even internal elements like processor, storage device, and memory. The software has to connect with the hardware units to complete the process.
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The computer will only boot after the POST process is successful. Problems in a computer can certainly appear after the POST process like windows hanging during start-up but most of the time those problems are related to computers operating system or software problem, not a hardware one.
The checks performed are on the following:
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Hardware components like processor, storage device, and memory.
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Basic system devices like keyboard and mouse.
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CPU registers.
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DMA or direct memory access.
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Timer.
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Interrupt controller.
If the POST finds something wrong during the test you will receive an error of some kind, displayed on your screen, one clear enough to help you jump-start the troubleshooting process.
How are the problems displayed?
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Just about anything that stops a computer from starting will come up. The error messages could consist of text messages on the device or in the form of beeps.
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Errors are displayed in the form of flashing LEDs, audible beeps, or error messages on the monitor which are basically referred to as POST codes, BEEP codes, and on-screen POST error messages, respectively.
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On mac computers, POST errors often appear as an icon or any other graphic instead of an actual error message. For example, a broken folder icon after starting your mac means that a computer can not find a suitable hard drive to boot from.
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Certain types of failure might not produce an error message at all or they may be hidden behind the manufacturer's logo.
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The error messages can range from a screen problem to a faulty motherboard
Examples for beep mode on a mac are:
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No RAM installed/detected.
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Incompatible RAM devices.
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The processor is not usable.
What are the POST code indicators and their meaning?
1. Short Beep
Normal post: the system is OK.
2. Sort Beeps
Post errors error code is shown on the screen.
3. No BEEP
Power supply, system problem, disconnected CPU, or disconnected speaker.
4. Continuous beep
Ram or keyboard problem.
5. Repetitive short beeps
Power supply, system board, or keyboard problem.
6. 1 long and 1 short beep
System board problem.
7. 1 long and 2 short beeps
Display adapter problem
8. 1 long and 3 short beeps
enhanced the graphic editor problem.
9. 3 long beeps
keyboard card problem
Conclusion
The above article covers everything you need to know about POST. The article covers everything such as What is POST and its full form, the role of the post, types of problem encountered, and POST code indicators and their meaning.
Frequently Asked Questions
1: What is P.O.S.T. in a computer?
P.O.S.T. stands for Power-On Self Test. It is a diagnostic process that a computer performs when it is powered on to check the hardware components for proper functioning.
2: What are the types of P.O.S.T. errors?
There are generally two types of P.O.S.T. errors: fatal and non-fatal. Fatal errors halt the boot process and prevent the computer from starting up, while non-fatal errors are less severe and allow the computer to continue booting up.
3: What are some common causes of P.O.S.T. errors?
Common causes of P.O.S.T. errors include faulty hardware components, incorrect BIOS settings, incompatible hardware, and power supply issues.
4: How can I troubleshoot P.O.S.T. errors?
To troubleshoot P.O.S.T. errors, try reseating the hardware components, resetting the BIOS to default settings, checking for hardware compatibility, and ensuring that the power supply is working correctly. If the issue persists, you may need to replace faulty hardware components or seek professional assistance.
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