Int 15/AX=2403h

SYSTEM - later PS/2s - QUERY A20 GATE SUPPORT

AX = 2403h

Return:
CF clear if successful
AH = 00h
BX = status of A20 gate support (see #00462)
CF set on error
AH = status
01h keyboard controller is in secure mode
86h function not supported

Notes: Also supported by AMI PCI BIOS and Qualitas 386MAX v6.01+. IBM classifies this function as optional

BUG: At one point early in processing INT 15/AH=24h, the AMI PCI BIOS version 1.00.05.AX1 compares whether AL==03h instead of AL>=03h, thus causing a random branch on any value of AL greater than 3.

See Also: AX=2402h

Bitfields for A20 gate support status: Bit(s) Description (Table 00462) 0 supported on keyboard controller 1 supported with bit 1 of I/O port 92h 14-2 reserved 15 additional data is available (location not yet defined)

Category: Vendor-specific BIOS Extensions - Int 15h - S

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