In computing, a postcard is a card that reports error codes produced by a POST. They are easy to use, just insert one into an available expansion slot. Postcards are available in ISA, PCI and AGP variants. The card reports either a hexadecimal number or a pattern of LEDs. The code depends on the motherboard. A book of reference tables usually accompany the card and can tell what is wrong. These can cover a large range of motherboard manufacturers, as different BIOSes use different codes. Postcards are often used by technicians to troubleshoot computers that refuse to boot. Some motherboards come with a built in display to diagnose hardware problems.
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