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In computing, a POST card is a plug-in diagnostic interface card that displays progress and error codes generated during power-on self-test (POST) of a computer. It is used to troubleshoot computers that do not start up.
At a minimum, if the CPU, BIOS, and the I/O interface upon which the POST card relies on are all working, a POST card can be used to monitor the system's Power-On Self Test (POST), or to diagnose problems with it. The system introduced on IBM PC computers sends 8-bit byte codes (usually displayed as two hexadecimal digits) to a specified I/O port (usually 80 hex) during startup, some indicating a stage in the startup procedure, others identifying errors. The description for each code must be looked up in a table for the particular BIOS. For example, for the 1984 IBM PC/AT code 1D is issued when about to Determine Memory Size Above 1024K, and code 2D in the event of 8042 Keyboard Controller Failure, 105 System Error. If startup does not complete successfully, either an error code, or the code of the last operation performed, is available.
POST cards provide information even when a standard display is not available, either because connecting a monitor is impractical, or because the failure occurs before the video subsystem is operational.
POST cards are inserted into an expansion slot, and are available with connectors for the ISA (also supporting EISA), 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 headers 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 debug port common on USB 2.0 EHCI controllers. [1]
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' [2] [1] and independent websites.
In addition to displaying numeric codes, many cards monitor power supply voltages, clock and oscillator signals, reset signal, and other parameters. [3]
Diagnostic cards are today mainly used by designers of motherboards and extension cards, along with logic analyzers and other debug tools and interfaces. They are less commonly used in the 21st century for computer repair and by system integrators, but remain available. POST cards for PCs, while originally high-priced, cost from just a few US dollars upwards in the 21st century.
Some motherboards have a built-in display to diagnose hardware problems. Most also report POST errors with audible beeps, if a PC speaker is attached. Such motherboards make POST cards less necessary.
When these diagnostic cards were first introduced motherboards were expensive and well worth troubleshooting and repairing. By the late twentieth century large scale integration, mass production made motherboards inexpensive components. Motherboards were rarely repaired, but replaced; the main purpose of a POST card is to determine that parts mounted on the motherboard itself, rather than plugged-in video cards, RAM, etc. are at fault.
Accelerated Graphics Port (AGP) is a parallel expansion card standard, designed for attaching a video card to a computer system to assist in the acceleration of 3D computer graphics. It was originally designed as a successor to PCI-type connections for video cards. Since 2004, AGP was progressively phased out in favor of PCI Express (PCIe), which is serial, as opposed to parallel; by mid-2008, PCI Express cards dominated the market and only a few AGP models were available, with GPU manufacturers and add-in board partners eventually dropping support for the interface in favor of PCI Express.
Industry Standard Architecture (ISA) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088-based IBM PC, including the IBM PC/XT as well as IBM PC compatibles.
A motherboard is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It holds and allows communication between many of the crucial electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. Unlike a backplane, a motherboard usually contains significant sub-systems, such as the central processor, the chipset's input/output and memory controllers, interface connectors, and other components integrated for general use.
Peripheral Component Interconnect (PCI) is a local computer bus for attaching hardware devices in a computer and is part of the PCI Local Bus standard. The PCI bus supports the functions found on a processor bus but in a standardized format that is independent of any given processor's native bus. Devices connected to the PCI bus appear to a bus master to be connected directly to its own bus and are assigned addresses in the processor's address space. It is a parallel bus, synchronous to a single bus clock. Attached devices can take either the form of an integrated circuit fitted onto the motherboard or an expansion card that fits into a slot. The PCI Local Bus was first implemented in IBM PC compatibles, where it displaced the combination of several slow Industry Standard Architecture (ISA) slots and one fast VESA Local Bus (VLB) slot as the bus configuration. It has subsequently been adopted for other computer types. Typical PCI cards used in PCs include: network cards, sound cards, modems, extra ports such as Universal Serial Bus (USB) or serial, TV tuner cards and hard disk drive host adapters. PCI video cards replaced ISA and VLB cards until rising bandwidth needs outgrew the abilities of PCI. The preferred interface for video cards then became Accelerated Graphics Port (AGP), a superset of PCI, before giving way to PCI Express.
PC Card is a parallel peripheral interface for laptop computers and PDAs.
In computing, an expansion card is a printed circuit board that can be inserted into an electrical connector, or expansion slot on a computer's motherboard to add functionality to a computer system. Sometimes the design of the computer's case and motherboard involves placing most of these slots onto a separate, removable card. Typically such cards are referred to as a riser card in part because they project upward from the board and allow expansion cards to be placed above and parallel to the motherboard.
On computers, a serial port is a serial communication interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in parallel. Throughout most of the history of personal computers, data has been transferred through serial ports to devices such as modems, terminals, various peripherals, and directly between computers.
A graphics card is a computer expansion card that generates a feed of graphics output to a display device such as a monitor. Graphics cards are sometimes called discrete or dedicated graphics cards to emphasize their distinction to integrated graphics processor on the motherboard or the CPU. A graphics processing unit (GPU) that performs the necessary computations is the main component in a graphics card, but the acronym "GPU" is sometimes also used to erroneously refer to the graphics card as a whole.
PCI Express, officially abbreviated as PCIe or PCI-e, is a high-speed serial computer expansion bus standard, designed to replace the older PCI, PCI-X and AGP bus standards. It is the common motherboard interface for personal computers' graphics cards, sound cards, hard disk drive host adapters, SSDs, Wi-Fi and Ethernet hardware connections. PCIe has numerous improvements over the older standards, including higher maximum system bus throughput, lower I/O pin count and smaller physical footprint, better performance scaling for bus devices, a more detailed error detection and reporting mechanism, and native hot-swap functionality. More recent revisions of the PCIe standard provide hardware support for I/O virtualization.
SATA is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard to become the predominant interface for storage devices.
In a computer system, a chipset is a set of electronic components on one or more integrated circuits that manages the data flow between the processor, memory and peripherals. The chipset is usually found on the motherboard of computers. Chipsets are usually designed to work with a specific family of microprocessors. Because it controls communications between the processor and external devices, the chipset plays a crucial role in determining system performance.
The southbridge is one of the two chips in the core logic chipset on older personal computer (PC) motherboards, the other being the northbridge. As of 2023, most personal computer devices no longer use a set of two chips, and instead have a single chip acting as the 'chipset', for example Intel's Z790 chipset.
ExpressCard, initially called NEWCARD, is an interface to connect peripheral devices to a computer, usually a laptop computer. The ExpressCard technical standard specifies the design of slots built into the computer and of expansion cards to insert in the slots. The cards contain electronic circuits and sometimes connectors for external devices. The ExpressCard standard replaces the PC Card standards.
PCI-X, short for Peripheral Component Interconnect eXtended, is a computer bus and expansion card standard that enhances the 32-bit PCI local bus for higher bandwidth demanded mostly by servers and workstations. It uses a modified protocol to support higher clock speeds, but is otherwise similar in electrical implementation. PCI-X 2.0 added speeds up to 533 MHz, with a reduction in electrical signal levels.
A power-on self-test (POST) is a process performed by firmware or software routines immediately after a computer or other digital electronic device is powered on.
PC/104 is a family of embedded computer standards which define both form factors and computer buses by the PC/104 Consortium. Its name derives from the 104 pins on the interboard connector (ISA) in the original PC/104 specification and has been retained in subsequent revisions, despite changes to connectors. PC/104 is intended for specialized environments where a small, rugged computer system is required. The standard is modular, and allows consumers to stack together boards from a variety of COTS manufacturers to produce a customized embedded system.
The AMD 700 chipset series is a set of chipsets designed by ATI for AMD Phenom processors to be sold under the AMD brand. Several members were launched in the end of 2007 and the first half of 2008, others launched throughout the rest of 2008.
In electronic systems a diagnostic board is a specialized device with diagnostic circuitry on a printed circuit board that connects to a computer or other electronic equipment replacing an existing module, or plugging into an expansion card slot.
I/O Controller Hub (ICH) is a family of Intel southbridge microchips used to manage data communications between a CPU and a motherboard, specifically Intel chipsets based on the Intel Hub Architecture. It is designed to be paired with a second support chip known as a northbridge. As with any other southbridge, the ICH is used to connect and control peripheral devices.
M.2, pronounced m dot two and formerly known as the Next Generation Form Factor (NGFF), is a specification for internally mounted computer expansion cards and associated connectors. M.2 replaces the mSATA standard, which uses the PCI Express Mini Card physical card layout and connectors. Employing a more flexible physical specification, M.2 allows different module widths and lengths, which, paired with the availability of more advanced interfacing features, makes M.2 more suitable than mSATA in general for solid-state storage applications, particularly in smaller devices such as ultrabooks and tablets.