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156 Chapter 4
* If the BIOS detects error 2C, 2E, or 30 (base 512K RAM error), it displays an additional word-bitmap (xxxx)
indicating the address line or bits that failed. For example, 2C 0002 means address line 1 (bit one set) has
failed. 2E 1020 means data bits 12 and 5 (bits 12 and 5 set) have failed in the lower 16 bits. Note that error 30
cannot occur on 386SX systems because they have a 16 rather than 32-bit bus. The BIOS also sends the
bitmap to the port-80 LED display. It first displays the check point code, followed by a delay, the high-order
byte, another delay, and then the low-order byte of the error. It repeats this sequence continuously.
E2h Initialize the CPU
E3h Initialize system timer
E4h Initialize system I/O
E5h Check force recovery boot
E6h Checksum BIOS ROM
E7h Go to BIOS
E8h Set Huge Segment
E9h Initialize Multi Processor
EAh Initialize OEM special code
EBh Initialize PIC and DMA
ECh Initialize Memory type
EDh Initialize Memory size
EEh Shadow Boot Block
EFh System memory test
F0h Initialize interrupt vectors
F1h Initialize Run Time Clock
F2h Initialize video
F3h Initialize System Management Mode
F4h 1 Output one beep before boot
F5h Boot to Mini DOS
F6h Clear Huge Segment
F7h Boot to Full DOS
Code Beeps For Boot Block in Flash ROM