Motherboards POST codes Tester (POST card).
This product is cardinally different from the existing analogues of this price bracket provided with more attractive display, supplementary protection against hang-up. It works under any BIOS, on any motherboard with PCI-slot.
POST Code Dual Indicators are located on the both (two) sides of the board, that allows peeking the breakpoint of the motherboard without unscrewing it from the chassis. The location of informational electroluminescent diodes, that register +3.3V, +5V, +12V and Г12V, has been also changed, as well as the reset signal condition (blanc electroluminescent diode shows active state).
If the indicator illuminates only a single numeric character, that means that Clock signal is missing on this PCI-slot. Usually the signal disappears after BIOS initialization.
The main purpose of POST procedure is testing of devices true functionality and heading initiation of main units and sub-systems before operational system loading (such as processor, memory and other motherboard devices, video controller, keyboard controllers, FDD and HDD controllers etc.)which is necessary for further computer.
Before the beginning of every operation POST procedure generates special code of 1 byte (from 00 till FFh), named POST-code and records its value to the special diagnostic port in address space of Input/Output devices (the port with address 80h is reserved for this purpose in IBM PC/AT computers types).
If during proving or initialization of devices the fatal error appears, further POST procedure operation is stopped and POST-code, which was put into the diagnostic port beforehand, determines uniquely the operation, where POST procedure breakpoint has taken place, thus defective device. In case if the error is not fatal, a signal sounds, and POST procedure continues further operation.
However, it should be taken into consideration that POST-codes tables are different for BIOS of various manufacturers, and in view of appearance of new testing devices and chipsets, are a little bit different even for different BIOS versions of the same manufacturer.
Original and true POST-codes tables can be found at the correspondent BIOS manufacturers sites: «AMI» and «Award». Sometimes, POST-codes tables are listed in the motherboards manuals.