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Chapter 8 BIOS ROM
Compaq Deskpro 4000N and 4000S Personal Computers
First Edition - September 1997
8-12
8.4.3 TEMPERATURE SENSOR
A temperature sensor component is mounted in the cavity of the microprocessor socket. This
sensor component detects when the microprocessor has reached a programmed temperature level
and initiates appropriate action. The sensor is programmed by BIOS for two temperature levels; a
level for initiating a caution to the user and another level to initiate a system shutdown. Detection
of a temperature level results in asserting an IRQ and/or the SMI- for initiating action.
The sensing feature is set up by BIOS during POST. A particular microprocessor step will have
peculiar operating temperature optimums so that a processor upgrade may require that the BIOS
be upgraded as well. The status of the temperature condition (caution, critical) may be retrieved
using the INT 15, AX=E816h call.
8.4.4 DRIVE FAULT PREDICTION
The Compaq BIOS provides direct Drive Fault Prediction support for IDE-type hard drives. This
feature is provided through two BIOS calls. Function INT 15, AX=E817h is used to retrieve a
512-byte block of drive attribute data while the INT 15, AX=E81Bh is used to retrieve the drive’s
warranty threshold data. If data is returned indicating possible failure then the following
message is displayed:
“1720-Intellisafe Hard Drive detects imminent failure”