Int 1A/AX=8100h

AX = 8100h

Return:
AL > 80h if supported
AX = 00C4h if supported (1000SL/TL)
CF set if sound chip is busy
CF clear  if sound chip is free

Note: The value of CF is not definitive; call this function until CF is clear on return, then call AH=84h"Tandy"