Int 13/AH=2Dh

AH = 2Dh
AL = new state (00h disabled, 01h enabled)

Return:
AX = status (0000h successful)

Desc: Specify whether the cache should attempt to read ahead of actual requests

Note: This function enables or disables read-ahead for all drives; use AH=37h to change a single drive

See Also: AH=2Ch - AH=37h