Appendix D POST LEDs 75
Code Name Description of check-point
0B Test CMOS RAM Test CMOS RAM checksum. If bad or
insert key pressed, INT OOh-1Fh
according to INT_TBL.
0C Initialize keyboard detect type of keyboard controller
(optional). Set num_lock status.
0D Initalize video interface Detect CPU clock. Read interface CMOS
location 14h to find out type of video in
use. Detect and initialize video adaptor.
0E Test video memory Test video memory, write sign-on
message to screen. Set up shadow RAM-
enable according to setup.
0F Test DMA controller 0 BIOS checksum test. Keyboard detection
and initialization.
10 Test DMA controller 1
11 Test DMA page registers Test DMA page registers.
12-13, 1B, 1E Reserved
14 Test timer counter 2 Test 8254 timer 0 counter 2.
15 Test 8259-1 mask bits Verify 8259 channel 1 masked interrupts
by alternately turning off and on the
interrupt lines.
16 Test 8259-2 mask bits Verify 8259 channel 2 masked interrupts
by alternately turning off and on the
interrupt lines.
17 Test 8259-1 mask bits Turn off interrupts then verify no interrupt
mask register is on.
18 Test 8259 interrupt Force an interrupt and verify the function-
ality interrupt occurred.
19 Test stuck NMI bits Verify NMI can be cleared.
(parity/IO check)
1A Display CPU clock
20 Enable slot 0 Initialize slot 0 (system board).
21-2F Enable slots 1-15 Initialize slots 1 through 15.
30 Size base and extended Size base memory from 256 KB to
memory 640 KB and extended memory above
1 MB.
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