5 Power-On Self-Test and Error Messages

Order in Which the Tests are Performed

 

 

Tests the system ROM BIOS and shadows it. Failure to shadow the ROM

Shadow the System ROM BIOS

BIOS will cause an error code to display. The boot process will continue, but

the system will execute from ROM. This test is not performed after a soft

 

 

 

 

reset (using

 

 

 

 

 

 

 

and Delete ).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Load CMOS Memory

Checks the serial EEPROM and returns an error code if it has been

 

corrupted. Copies the contents of the EEPROM into CMOS RAM.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CMOS RAM Test

Checks the CMOS RAM for start-up power loss, verifies the CMOS RAM

 

checksums. Test failure causes error codes to display.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CPU Cache Memory Test

Tests the processor’s internal level-one cache RAM. Test failure causes an

 

error code to display and the boot process to abort.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Video Tests

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Initializes the video subsystem, tests the video shadow RAM, and, if

 

Initialize the Video

required, shadows the video BIOS. A failure causes an error code to display,

 

 

but the boot process continues.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

System Board Tests

 

 

 

 

 

 

 

 

 

 

 

 

 

8042 Self-Test

Downloads the 8042 and invokes the 8042 internal self-test. A failure

 

causes an error code to display.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Timer 0/Timer 2 Test

Tests Timer 0 and Timer 2. Test failure causes an error code to display.

 

 

 

 

 

 

 

 

 

 

 

 

DMA Subsystem Test

Checks the DMA controller registers. Test failure causes an error code to

 

display.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Tests the Interrupt masks, the master controller interrupt path (by forcing

 

Interrupt Controller Test

an IRQ0), and the industry-standard slave controller (by forcing an IRQ8).

 

 

Test failure causes an error code to display.

 

 

 

 

 

 

 

 

 

 

 

 

Real-Time Clock Test

Checks the real-time clock registers and performs a test that ensures that

 

the clock is running. Test failure causes an error code to display.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Audio Test

If the audio board is present, invokes a built-in self-test. Test failure causes

 

an error code to display.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Memory Tests

 

 

 

 

 

 

 

 

 

 

 

 

 

RAM Address Line

Verifies the address independence of real-mode RAM (no address lines stuck

 

Independence Test

together). Test failure causes an error code to display.

 

 

 

 

 

 

 

 

 

 

 

 

 

Sizes and clears the protected mode (extended) memory and writes the

 

Size Extended Memory

value into CMOS bytes 30h and 31h. If the system fails to switch to

 

 

protected mode, an error code is displayed.

 

 

 

 

 

 

 

 

 

 

 

 

 

Read/write test on real-mode RAM. (This test is not done during a reset

Real-Mode Memory Test (First

using

 

 

 

 

and

Delete ). The test checks each block of

 

 

 

 

 

 

 

 

 

640KB)

system RAM to determine how much is present. Test failure of a 64 KB

 

 

block of memory causes an error code to display, and the test is aborted.

 

 

 

 

 

 

 

 

 

 

 

 

 

Tests shadow RAM in 64 KB segments (except for segments beginning at

 

Shadow RAM Test

A000h, B000h, and F000h). If they are not being used, segments C000h,

 

 

D000h and E000h are tested. Test failure causes an error code to display.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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