Why are POST cards used?
A POST card is type of a plug-in interface card. It is primarily used with BIOS in order to display the progress of a POST. A POST is a Power-On Self-Test, which primarily used to diagnose that the BIOS is running smoothly and is able to communicate with the attached hardware.
In case, the BIOS is not running smoothly, an error message is displayed on the screen. A POST card is responsible for displaying the error codes that are generated during the POST. It is also used to troubleshoot computers that do not start up.