Editing POST card (section)

==Operation==
POST cards are inserted into an expansion slot, and are available with connectors for the [[Industry Standard Architecture|ISA]] (also supporting [[Extended Industry Standard Architecture|EISA]]), [[Peripheral Component Interconnect|PCI]], [[PCI Express]], Mini [[PCIe]] (for laptops), [[Universal Serial Bus]], or [[Low Pin Count]] bus, or for a parallel port. A typical card for desktop computers has a different bus interface on each edge; a card for laptop computers may have both a miniPCI and a parallel port connector (plus USB to supply power).

Modern motherboards often do not broadcast POST codes to their PCI Express slots (PCIe switches only pass on transactions after having been configured to do so by the BIOS). On such motherboards, the [[Low Pin Count]] (LPC) bus, an ISA variant normally used to connect a [[Trusted Platform Module]] (TPM), may be the only bus where POST messages can still be seen. However LPC connectors are not standardized, with between 9 and 19 pins and both 2.54 mm and 2 mm [[pin header]]s commonly used. Therefore, an LPC POST card may have to auto-detect first the pin assignment used.

Another option are USB POST cards such as AMI Debug Rx, which use the [[EHCI debug port|debug port common on USB 2.0 EHCI controllers]].<ref name=aptio />

Information on the meaning of POST codes for different BIOSes is needed to interpret the codes. This may be supplied with cards, but becomes dated as later BIOSes are issued; more up-to-date information may be available on manufacturers'<ref>{{cite web|url=https://www.asus.com/support/FAQ/1039406/|title=General Qcode / Q-code / Post Code table for ASUS motherboards|access-date=2019-07-31}}</ref><ref name=aptio>{{cite web|url=https://ami.com/ami_downloads/Aptio_V_Status_Codes.pdf|title=Aptio 5.x status codes|publisher=American Megatrends|access-date=2019-07-19}}</ref> and independent websites.

In addition to displaying numeric codes, many cards monitor power supply voltages, clock and oscillator signals, reset signal, and other parameters.<ref>[https://www.passmark.com/products/pci-post-card-pro.htm An example of a POST diagnostic card which tests several parameters in addition to the hex codes]</ref>