Hardware Reference
In-Depth Information
to standard Advanced Power Management control, but problems can also cause a lockup
with either a red or blue screen with an ACPI error code.
Red screens indicate that the problem is probably related to hardware or the BIOS. Blue
screens, on the other hand, indicate that the problem is probably related to software or is
an obscure problem. The ACPI error codes are described in
Table 5.25
.
Table 5.25 ACPI Error Codes
Virtually all these errors are the result of partial or incomplete ACPI implementations or
incompatibilitiesineithertheBIOSordevicedrivers.Ifyouencounteranyoftheseerrors,
contact your motherboard manufacturer for an updated BIOS or the device manufacturers
for updated drivers.
BIOS/MBR Error Messages
When a PC system is first powered on, the system runs a POST. If errors are encountered
during the POST, you usually see a text error message displayed onscreen. Errors that oc-
cur early in the POST might happen before the video card is initialized. These types of
errorscan'tbedisplayed, sothe system uses twoother alternatives forcommunicating the
error message. One is beeping—the system beeps the speaker in a specific pattern that in-
dicates which error has occurred.
For detailed lists of the BIOS POST beep codes,
see
Chapter 20
, “
PC Diagnostics,
Testing, and Maintenance
,”
p.
961
.
The alternative is to send a hexadecimal error code to I/O port address 80h, which can
be read by a special card in one of the bus slots. When the ROM BIOS is performing the
POST, in most systems the results of these tests are continuously sent to I/O port 80h so
special diagnostics cards called
POST cards
can monitor them (see
Figure 5.10
). These
tests sometimes are called
manufacturing tests
because they were designed into the sys-
tem for testing it on the assembly line without a video display attached.
Figure 5.10
A two-digit hexadecimal code display (left) and a POST card in operation (right).
