Int 15 Fn 2401 - System - Later Ps/2s - Enable A20 Gate [b] AX = 2401h Return: CF clear if successful AH = 00h CF set on error AH = status 01h keyboard controller is in secure mode 86h function not supported Note: also supported by Qualitas 386MAX v6.01+ See Also: AX=2400h,AX=2402h