POST-card (sometimes called a POST-tester or POST-card) - an expansion board that has its own digital indicator and displays the initialization codes of the motherboard on it. From the last code displayed, you can determine which component has a malfunction. These codes depend on the motherboard BIOS manufacturer. If there are no errors and the test passes normally, the POST displays a value that does not change during the operation of the computer depending on the BIOS version, for example, on most boards, when the initialization is completed, the FF code is issued.
The POST tester can be performed in many ways. For example, POST Code Dual has a display indicator on both sides, so there is no need to remove the motherboard to read the information from the indicator. Also, all POST testers have LEDs that indicate the presence of voltage +5 +3.3 +12, −12 and a RESET signal LED (meaning not rebooting with the Reset button). Other indicators are sometimes added. POST testers have different connectors for connecting, for example, PCI , ISA (older models), miniPCI (laptops) and even LPT (for motherboards that transmit a POST signal to the LPT port).
The POST signal output port is 80h, but there may be others (by the way, some testers have a port setting), most often 81h.
See also
- Post
- Computer boot