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A20 Gate Status Byte Flags
7: %define GATE_A20_DISABLED 0x01 ;Bit 0, set if A20 is disabled 8: %define GATE_A20_FORCE_DISABLE 0x02 ;Bit 1, set if A20 is meant to be disabled for fault tolerance testing purposes
A20 State Change Method
13: %define GATE_A20_METHOD_failed 0x00 ;None of the methods attempted were successfull 14: %define GATE_A20_METHOD_none 0x01 ;A20 was in correct state before boot loader started 15: %define GATE_A20_METHOD_BIOS 0x02 ;A20 state changed by BIOS function (Int 0x15, AX = 0x2401 or Int 0x15, AX = 0x2400) 16: %define GATE_A20_METHOD_PS2 0x03 ;A20 state changed by PS/2 controller chip 17: %define GATE_A20_METHOD_FAST 0x04 ;A20 state changed by "Fast A20" method