Int 15 Fn C8  - System - Enable/disable Processor Functions                [B]

   AH = C8h
   AL = function
       00h disable cache or (90 and 95) disable cache L1
       01h enable cache or (90 and 95) enable cache L1
       ---models 90 and 95 only---
       02h disable cache L2
       03h enable cache L2
       04h disable both caches
       05h enable both caches
       06h return status of both caches
       07h-FFh Reserved

Return: CF set on error
   CF clear if successful
       AH = status (see below)
   For subfunction 06h only:
       BH = status of cache L2
       00h enabled
       01h disabled or not installed
       BL = status of cache L1 (same codes as BH)

Notes:  supported by at least PS/2 70, 70/486, 80-A21, 90, 95
   call AH=C0h and examine bit 3 of feature byte 2 to check if this
     function is supported.
   on a 486 system, any external caches must be disabled when the
     on-chip cache (L1) is disabled.

See Also: AH=C0h

Values for status:
 00h   operation successful
 01h   function choice (in AL) is invalid
 02h   NVRAM data is invalid
 03h   cache test error
 04h   (90 and 95 only) cannot perform operation requested due to state of
     other cache (see note above)
 05h   no L2 cache is present