XMS 08H: Query Free Extended Memory

                                                     Compatibility: XMS 2.0+ 
 Expects: AH    08H
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 Returns: AX    size of largest free XMB, in kbytes
          BL    XMS error code (if BL >= 80H)
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    Info: This obtains the size, in K-bytes, of the largest free block of
          extended memory.

   Notes: The 64K-16 bytes of the HMA▲ are not included in this
          calculation.

See Also: XMS Functions
          Extended Memory Specification (XMS)
          DOS Functions
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