Category: <b>BIOS</b>
<p>
<pre><b>INT 15 - SYSTEM - later PS/2s - EXPANSION UNIT, RETURN CONFIGURATION NUMBER</b>

	AX = 5101h
Return: CF set if successful
	    AH = 00h
	    AL = current configuration number
		00h system unit only
		FFh configuration not recognized
	    BX = status flag
		bits 0-14: reserved
		bit 15: additional data is available (location TBD)
	CF clear on error
	    AH = status
		01h expansion unit is not present
		86h function not supported
Note:	CF convention is the reverse of the standard convention for this
	  interrupt.  (Perhaps a typo in the IBM BIOS Tech Ref?)
</pre>