Hardware Reference
In-Depth Information
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Peripheral diagnostics software
—Manyhardware devices shipwith specialized dia-
gnostics software designed to test their particular functions. Adaptec SCSI host ad-
apters,forexample,includediagnosticfunctionsinthecard'sROMBIOSthatyoucan
accesswithakeystroke(Ctrl+A)atboottime.Otherdevicesoradaptersmightprovide
a diagnostic program or disk, usually included with the drivers for the device.
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Operating system diagnostics software
—Operating systems such as Windows,
Linux, and so on often include a variety of diagnostic software utilities designed to
identify and monitor the performance of various components in the computer.
•
Commercial diagnostics software
—A number of manufacturers make general-pur-
pose diagnostics software for PCs. This type of software is often bundled with other
system maintenance and repair tools to form a general PC software toolkit.
•
Free/open-source diagnostics software
—A large number of free or open-source dia-
gnosticprogramsareavailableforPCs,includingsmalltask-specificprogramsaswell
as complete collections of diagnostics in bootable form.
The POST
When IBM began shipping the original PC in 1981, it included safety features that had
neverbeenseeninapersonalcomputer.ThesefeatureswerethePOSTandparity-checked
memory. Although parity-checked or even error-correcting code (ECC) memory is no
longer available in most low-end chipsets, every PC still executes a POST when you
turn it on. The following sections provide more detail on the POST, a series of program
routines buried in the motherboard ROM-BIOS chip that tests all the main system com-
ponents at power-on time. This series of routines is partially responsible for the delay
when you turn on your PC; the computer executes the POST before loading the operating
system.
These tests check the primary components in your system, such as the CPU, ROM,
motherboard support circuitry, memory, and major peripherals such as the expansion
chassis. These tests are brief and are designed to catch hard (not intermittent) errors. The
POST procedures are not very thorough compared to available disk-based diagnostics.
The POST process provides error or warning messages whenever it encounters a faulty
component.
Although the diagnostics performed by the system POST are not very thorough, they are
the first line of defense, especially when it comes to detecting severe motherboard prob-
lems. If the POST encounters a problem severe enough to keep the system from operating
properly, it halts the system boot process and generates an error message that often iden-
tifies the cause of the problem. These POST-detected problems are sometimes called
fatal
errors
because they prevent the system from booting.
