INT 16 U - Netroom CACHECLK - INSTALLATION CHECK
        AX = 5758h
        BX = 4858h ('HX')
        DX = 4443h ('DC')
        CX <> 5758h
Return: BX = 6878h if installed
        CX = 6463h if installed
            AX = code segment of TSR
            CX = internal version??? (v3.00 returns 0100h)
Program: CACHECLK is a "cloaked" disk cache included with Netroom
Notes:  if CX=5758h on entry, CACHECLK returns with all registers unchanged
        the cache statistics are located early in the segment pointed at by
          AX on return

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