INT 7F - CONVERGENT TECHNOLOGIES ClusterShare CTOS ACCESS VECTOR
        AL = request ID
            01h "Request"/"RequestDirect"
                ES:BX -> pRq
                DX ignored
            04h "Wait"
                ES:BX -> ppMsgRet
                DX = exchange
            05h "AllocExch"
                ES:BX -> pExchRet
            06h "DeAllocExch"
                DX = exchange
            07h "Check"
                ES:BX -> ppMsgRet
                DX = exchange
        CX = 4354h ('CT')
Return: AX = status
            0000h successful