POSTs are a type of internal tests that machines perform when they start or reset. POST is a program that checks if the microprocessor works as intended by running some simple and fast operations.
By storing some info in the ROM and then reading it, it can also test each byte of memory by checking the patterns in and on it.
Technipages Explains Power-On Self-Test (Post)
The internal tests that are part of POST are designed to test as much computer functionality as possible. They also include a check of every connected devices – they check if the keyboard responds, if the connected drives work, and if a printer responds to a request.
The more core tests – those that target the CPU and memory – are the main purpose of the POST checks. While peripherals can ultimately be replaced easily and usually aren’t a necessity in order for the machine to run.
One of the last checks performed is the search for a BIOS. POST checks drive A for some form of operating system, if that fails it checks other drives instead. Once the POST check is complete, the machine does whatever it was instructed to – be that boot, reboot or something else entirely.
While personal computers utilise POST tests, so does other tech. They are run by appliances, used in avionics, even in medical equipment.
Whenever a device that uses them is powered on restarted, they run automatically. The results can be displayed on a screen or stored by a diagnostic tool. In cases where monitors are tested, functionality is usually present in order to still display results if the monitor doesn’t work – this could be a lamp, speaker or something else entirely.
Common Uses of Power-On Self-Test (Post)
- Power-On Self-Tests are a great way to check for functionality without requiring a user to perform manual checks.
- POST checks run automatically on power-up.
- POST testing is used across a variety of tech sectors.
Common Misuses of Power-On Self-Test (Post)
- POST checks run after certain actions such as closing a program or switching off the PC.