Patent Publication Number: US-7589624-B2

Title: Component unit monitoring system and component unit monitoring method

Description:
BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The present invention relates to a component unit monitoring system for monitoring the status of a component unit, and more particularly to a component unit monitoring system for monitoring the status of a component unit using a wireless IC tag. 
   (2) Description of the Related Art 
   Heretofore, a server computer holds component unit information and ancillary sensor information as initial information in a NVRAM (NonVolatile RAM) that is inherent to the server computer. When the component unit information is changed, the information stored in the NVRAM needs to be updated to reflect the change. Therefore, it has been tedious and time-consuming to manage the component unit information. For monitoring a sensor attached to a component unit of a server computer, it has been customary to employ a controller known as a BMC (Baseboard Management Controller) for centralized management. The user is naturally unable to access fault information of the sensor unless the server computer is turned on. 
   On some conventional computer systems, a sensor attached to a component unit is monitored using a BMC as follows: The BMC is connected to devices to be monitored (hereinafter referred to as component units) which are mounted on the computer system by a bus such as an SMBus (System Management Bus). Fault information produced by sensors is generally stored in a memory that is managed by the BMC. Because the fault information from the sensors is stored in the memory associated with the BMC, the user needs dedicated software to read the fault information from the memory. In addition, the user cannot read the stored fault information when the computer system is turned off. 
   The fault information of various component units is centrally managed by the single BMC. Accordingly, the user is unable to track down records of fault information of individual component units when they are removed from the computer system. For identifying a sensor associated with a component unit in an analysis of fault information managed by the MBC, the user has to acquire necessary information from the NVRAM inherent to the computer system. It has been tedious and time-consuming to manage VNRAM information generated for each of the component units. 
   Japanese laid-open patent publication No. 2004-078840 discloses a wireless tag and a telemetry system for writing a signal from a sensor into an EEPROM (Electrically Erasable Programmable ROM) in the wireless tag and sending sensor data on a reply frame to an inquiring machine. Although the wireless tag reads the signal from the sensor, sends the signal to the inquiring machine, and stores the signal, the wireless tag does not analyze the signal and does not store analytic results. 
   Japanese laid-open patent publication No. 2004-157715 discloses a method of generating a database for an electronic apparatus by acquiring component numbers which are assigned to respective components of the electric apparatus and serve as component identification data for identifying the components, from a data acquisition device, and storing the acquired component identification data in association with a manufacturer&#39;s serial number as apparatus identification data. According to the disclosed method, although component numbers are acquired and stored, status information of the component is not dynamically grasped. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a component unit monitoring system which is capable of acquiring status information of component units of a system to be monitored regardless of whether the system is turned on or not. 
   Another object of the present invention is to provide a component unit monitoring system which is capable of acquiring status information of component units when they are removed from a system to be monitored. 
   Still another object of the present invention is to provide a component unit monitoring system which is capable of dynamically grasping the configurational information of a system to be monitored. 
   Technical features of the present invention for achieving the above objects will be described below using reference characters in parentheses that are used in the description of preferred embodiments of the present invention. The reference characters are added herein merely to clarify the correspondence between the description of the scope of claims and the description of the preferred embodiments, and should not be used to interpret the scope of the present invention which is described in the scope of claims. 
   A component unit monitoring system according to the present invention has at least one independently installable component unit ( 2 ), a system management controller ( 3 ,  3 ′), a wireless transmission and reception controller ( 4 ) connected to the system management controller ( 3 ,  3 ′), for controlling communications between the system management controller ( 3 ,  3 ′) and a first wireless link ( 7 ), and a wireless IC tag ( 1 ,  1 ′) mounted on the component unit ( 2 ), for acquiring status information of the component unit ( 2 ), the wireless IC tag ( 1 ,  1 ′) being connected to the wireless transmission and reception controller ( 4 ) through the first wireless link ( 7 ). 
   The wireless IC tag ( 1 ,  1 ′) sends status information representing an installation history, a status value, etc. of the component unit ( 2 ) through the first wireless link ( 7 ) to the system management controller ( 3 ,  3 ′). The system management controller ( 3 ,  3 ′) analyzes the status information received from the wireless IC tag ( 1 ,  1 ′) and sends an analytic result through the first wireless link ( 7 ) to the wireless IC tag ( 1 ,  1 ′). The wireless IC tag ( 1 ,  1 ′) stores the analytic result received from the system management controller ( 3 ,  3 ′) as a history of chronological data. 
   The component unit monitoring system further includes a component control device ( 20 ) connected between the component unit ( 2 ) and the wireless IC tag ( 1 ,  1 ′). The system management controller ( 3 ,  3 ′) sends a first request signal for acquiring the status information of the component unit ( 2 ) to the wireless IC tag ( 1 ,  1 ′) through the first wireless link ( 7 ). The wireless IC tag ( 1 ,  1 ′) sends a second request signal to the component control device ( 20 ) in response to the first request signal from the system management controller ( 3 ,  3 ′). The component control device ( 20 ) acquires the status information from the component unit ( 2 ) in response to the second request signal from the wireless IC tag ( 1 ,  1 ′) and sends the status information to the wireless IC tag ( 1 ,  1 ′). The wireless IC tag ( 1 ,  1 ′) sends the status information received from the component control device ( 20 ) to the system management controller ( 3 ,  3 ′). 
   The wireless IC tag ( 1 ,  1 ′) has either a power supply ( 11 ) for generating electric energy from electromagnetic waves transmitted over a wireless link, or a power supply ( 11 ) comprising a cell. Therefore, the system management controller ( 3 ,  3 ′) and the wireless IC tag ( 3 ,  3 ′) operate on respective different power supplies. 
   The component unit monitoring system further includes an external wireless module ( 6 ) for acquiring configurational information from the system management controller ( 3 ,  3 ′) or the wireless IC tag ( 1 ,  1 ′) through a second wireless link ( 7 ). 
   The system management controller ( 3 ,  3 ′) of the component unit monitoring system according to the present invention is thus capable of dynamically identifying component units. When the system management controller ( 3 ,  3 ′) detects a fault, the system management controller ( 3 ,  3 ′) controls the wireless transmission and reception controller ( 4 ) to store fault information into wireless IC tag ( 1 ,  1 ′). When the component unit monitoring system is serviced for maintenance, the external wireless module ( 6 ) may be used to analyze fault information or identify a faulty component unit regardless whether the system connected to the component unit or the faulty component unit ( 2 ) is turned on or off. 
   As described above, the component unit monitoring system according to the present invention is capable of acquiring status information of a component unit of a system to be monitored regardless of whether the system is turned on or off. 
   The component unit monitoring system is also capable of acquiring status information of a component unit removed from a computer system. 
   Furthermore, the component unit monitoring system is capable of dynamically grasping the configurational information of a system to be monitored. 
   The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a component unit monitoring system according to a first embodiment of the present invention; 
       FIG. 2  is a block diagram of a wireless IC tag used in the component unit monitoring system according to the first embodiment of the present invention; 
       FIG. 3  is a block diagram of a BMC used in the component unit monitoring system according to the first embodiment of the present invention; 
       FIG. 4  is a block diagram showing an example in which a wireless IC tag is mounted on a DIMM; 
       FIG. 5  is a block diagram showing an example in which a wireless IC tag is mounted on a FAN; 
       FIG. 6  is a block diagram of an external wireless module of the component unit monitoring system according to the first embodiment of the present invention; 
       FIG. 7  is a diagram showing a memory map held by the wireless IC tag used in the component unit monitoring system according to the first embodiment of the present invention; 
       FIG. 8  is a diagram showing component configurational information stored in a BMC memory; 
       FIG. 9  is a sequence diagram of a sequence for detecting a component unit that is newly installed in a computer system according to the first embodiment of the present invention; 
       FIG. 10  is a diagram showing the formats of wireless packets used in the process of detecting a new component unit; 
       FIG. 11  is a flowchart of a process performed by the BMC for detecting a new component unit; 
       FIG. 12A  is a flowchart of a component identifying process for confirming a configuration of a computer system; 
       FIG. 12B  is a flowchart of a process of detecting a new component unit; 
       FIG. 13  is a sequence diagram of a sequence for detecting fault information of a component unit according to the first embodiment of the present invention; 
       FIG. 14  is a diagram showing the formats of wireless packets used in the fault information detecting process according to the first embodiment of the present invention; 
       FIG. 15  is a flowchart of a process performed by the BMC for monitoring fault information; 
       FIG. 16A  is a flowchart of an operation sequence of the wireless IC tag for notifying the BMC of the status of a component unit; 
       FIG. 16B  is a flowchart of a process performed by the wireless IC tag for saving the status value of a component unit; 
       FIG. 16C  is a flowchart of a process performed by the wireless IC tag for saving the fault information of a component unit; 
       FIG. 17  is a sequence diagram of an operation sequence of the external wireless module for acquiring status information; 
       FIG. 18  is a diagram showing the formats of wireless packets used in the status information acquiring process; 
       FIG. 19  is a flowchart of a process performed by the external wireless module for acquiring status information; 
       FIG. 20  is a flowchart of a process performed by the wireless IC tag for acquiring status information; 
       FIG. 21  is a block diagram of a wireless IC tag used according to a second embodiment of the present invention; 
       FIG. 22  is a block diagram of a BMC according to the second embodiment of the present invention; 
       FIG. 23  is a sequence diagram of a sequence for detecting fault information of a component unit according to the second embodiment of the present invention; 
       FIG. 24  is a diagram showing the formats of wireless packets used in the fault information detecting process according to the second embodiment of the present invention; 
       FIG. 25  is a flowchart of a process performed by a BMC for monitoring fault information according to the second embodiment of the present invention; and 
       FIG. 26  is a flowchart of a fault information notifying process performed by the wireless IC tag according to the second embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As smaller wireless IC (Integrated Circuit) tags are available in the art, it has become possible to install those wireless IC tags on component units mounted in one housing or component units that are connected to a computer system by cables. A wireless IC tag installed on a system may be energized by a power supply which is different from the power supply of the computer system. A component unit monitoring system according to the present invention is preferably used to monitor the statuses of component units in a computer system, e.g., faults which have occurred in the component units or an installation history of the component units in the computer system. 
   1st Embodiment 
   A component unit monitoring system according to a first embodiment of the present invention will be described below with reference to  FIGS. 1 through 16 . 
   The component unit monitoring system serves to monitor the status information of component units, e.g., a motherboard in a computer, a DIMM (Dual-In-line Memory Module) on the motherboard, a cooling fan (hereinafter referred to as “FAN”), a CPU, etc., of a server computer system used in a server. The status information comprises configurational information representing the manner in which the component units are mounted in the computer system and fault information representing faults of the component units. 
     FIG. 1  shows in block form the component unit monitoring system according to the first embodiment of the present invention. As shown in  FIG. 1 , the component unit monitoring system comprises BMC (Baseboard Management Controller)  3  serving as a system management controller, component units including DIMM  2 - 1 , FAN  2 - 2 , CPU  2 - 3 , and motherboard  2 - 4 , and wireless transmission and reception controller  4  connected to BMC  3 . BMC  3 , the component units excluding motherboard  2 - 4 , and wireless transmission and reception controller  4  are mounted on motherboard  2 - 4  which is connected to a computer system. The component unit monitoring system also includes wireless IC tags  1 - 1  through  1 - 4  connected to the respective component units. The component unit monitoring system further has external wireless module  6  for connecting a circuit outside of the computer system through wireless links  7  to wireless transmission and reception controller  4  and wireless IC tags  1 - 1  through  1 - 4 . The component units including DIMM  2 - 1 , FAN  2 - 2 , CPU  2 - 3 , and motherboard  2 - 4  will also be collectively referred to as “component unit  2 ”, and wireless IC tags  1 - 1  through  1 - 4  connected to the respective component units will also be collectively referred to as “wireless IC tag  1 ”. 
   Wireless IC tag  1  is connected to wireless transmission and reception controller  4  through wireless links  7 , and is controlled by BMC  3  to acquire status information of component unit  2 . Wireless transmission and reception controller  4  and antenna  5  connected thereto are mounted on motherboard  2 - 4 . However, wireless transmission and reception controller  4  and antenna  5  are not limited to being mounted on motherboard  2 - 4 , but may be positioned anywhere insofar as they can be connected to wireless IC tag  1  through wireless links  7 . Component unit  2  is not limited to DIMM  2 - 1 , FAN  2 - 2 , CPU  2 - 3 , and motherboard  2 - 4  either, but may be an external storage unit, a monitor, a printer, etc. connected through various I/Fs insofar as it is part of the computer system. 
   According to the first embodiment, wireless IC tag  1  comprises a passive wireless IC tag which is energized by electric energy received from wireless transmission and reception controller  4  or external wireless module  6  through wireless link  7 . Wireless transmission and reception controller  4  and external wireless module  6  operate on the multiple access principles to communicate with all wireless IC tags  1  in the computer system. BMC  3  and external wireless module  6  are capable of selectively controlling wireless IC tags  1  to obtain status information therefrom by inserting GUIDs (Global Unique Identifiers) of wireless IC tags  1  into data transmitted to wireless IC tags  1 . 
     FIG. 2  shows wireless IC tag  1  in block form. As shown in  FIG. 2 , wireless IC tag  1  has tag memory  10 , power supply  11 , tag control circuit  12 , transceiver unit  13 , and tag antenna  14  which are connected to each other by a bus. 
   Tag memory  10  comprises a read-write memory capable of reading data therefrom and writing data therein, and has a memory map. Various information generated by tag control circuit  12  is stored in the memory map. 
     FIG. 7  shows details of memory map  100 . As shown in  FIG. 7 , memory map  100  has component information area  101 , component status area  102 , status history area  103 , fault information history area  104 , and installation history area  105 . 
   Component information area  101  stores component information inherent to component unit  2  on which wireless IC tag  1  is mounted. The component information includes component GUID  111  for identifying component unit  2 , component type  112  representing the name and type of component unit  2 , and component description  113  including specifications and version information of component unit  2 . A sufficiently large value represented by about 2 to the 128th power is assigned to component GUID  111 , so that component GUID  111  can uniquely identify a component unit. Component type  112  is used to identify the type of a component such as a CPU, a DIMM, a FAN, etc. Component description  113  represents information for describing features of a component unit, and may have any format. The component information is initially written in component information area  101 . 
   Component status area  102  stores status value  121  representing the present status of component unit  2 . Status value  121  represents information obtained from status signal  21  (see  FIG. 2 ) that is supplied from component control device  20 . For example, status value  121  indicates the temperature or voltage of component unit  2 , or the rotational speed of FAN  2 - 2 . 
   Status history area  103  stores a history of chronological data representing successive status values  121  from component status area  102  as status values  132  at respective times  131 . Fault information history area  104  is an area for storing fault information representative of faults that occurred in component unit  2  on which wireless IC tag  1  is mounted. Specifically, fault information history area  104  stores a history of chronological data representing successive times  141  at which faults were detected on component unit  2 , faulty system GUIDs  142  representing identifiers of computer systems connected to component unit  2  which was faulty, and faulty types  143 . 
   Installation history area  105  is an area for storing a history of system information of computer systems which were connected to component unit  2  on which wireless IC tag  1  is mounted. Specifically, installation history area  105  stores a history of chronological data representing successive recognition times  151  at which component unit  2  was recognized as a new unit, system GUIDs  152  representing identifiers of computer systems connected to component unit  2 , and system description  153  representing specifications and version information of those computer systems. Based on the installation system information stored in installation history area  105 , it is possible to track down computer systems to which component unit  2  was connected. 
   Wireless IC tag  1  communicates with wireless transmission and reception controller  4  and external wireless module  6  through tag antenna  14 . In wireless IC tag  1 , which is a passive wireless IC tag, power supply  11  generates electric energy based on electromagnetic waves transmitted from wireless transmission and reception controller  4  and external wireless module  6 , and tag control circuit  12  and transceiver unit  13  operates based on the electric energy supplied from power supply  11 . 
   Tag control circuit  12  controls signals and data in wireless IC tag  1 . In response to a request for status information from BMC  3 , tag control circuit  12  sends a request signal for requesting status signal  21  from component control device  20  to acquire status information of component unit  2 . Transceiver unit  13 , which serves to input and output signals and data through tag antenna  14 , receives status signal  21  from component control device  20 . Transceiver unit  13  also modulates and demodulates signals and data that are input and output through tag antenna  14 . 
     FIG. 3  shows details of BMC  3  in block form. As shown in  FIG. 3 , BMC  3  has detection processor  31 , error determining unit  32 , notifying unit  33 , transceiver unit  34 , BMC control circuit  35 , and BMC memory  36  which are connected to each other by a communication bus. 
   Transceiver unit  34  is connected to wireless transmission and reception controller  4  through motherboard  2 - 4 . Transceiver unit  34  controls wireless transmission and reception controller  4  to communicate with wireless IC tags  1  and external wireless module  6  through antenna  5 . BMC  3  is controlled by a program such as an OS of the computer system through motherboard  2 - 4 . 
   Detection processor  31  analyzes data supplied from wireless IC tag  1  and determines whether component unit  2  connected to the computer system is a new component unit or not. If detection processor  31  judges that component unit  2  connected to the computer system is a new component unit, then detection processor  31  requests component information from wireless IC tag  1  and stores the component information received from wireless IC tag  1  as component configurational information in BMC memory  36  which is an internal memory of BMC  3 . 
     FIG. 8  shows details of component configurational information stored in BMC memory  36 . As shown in  FIG. 8 , the component configurational information comprises as many items of information as component units  2  detected by detection processor  31 , each including component detection time  200  at which component unit  2  was detected, component GUID  202  corresponding to component information, component type  203 , and component description  204 . 
   Error determining unit  32  analyzes data supplied from wireless IC tag  1 , determines whether component unit  2  has suffered a fault or not, and transmits the determined result through wireless link  7  to wireless IC tag  1 . When requested by a program of the computer system, i.e., system program  8 , or external wireless module  6 , notifying unit  33  notifies system program  8  or external wireless module  6  of the component configurational information stored in BMC memory  36 . 
   BMC control circuit  35  controls signals and data in BMC  3  and also controls operation of detection processor  31 , error determining unit  32 , and notifying unit  33 . Transceiver unit  34  controls various signals and data that are input and output between wireless transmission and reception controller  4  and system program  8 . 
     FIG. 4  shows an example in which wireless IC tag  1 - 1  is mounted on DIMM  2 - 1 . As shown in  FIG. 4 , DIMM  2 - 1  has memory chip  22  connected to memory controller  20 - 1  as component control device  20  through a memory bus. Wireless IC tag  1 - 1  is connected to memory controller  20 - 1  through a portion of the signal line of the memory bus. In response to a request from wireless IC tag  1 - 1 , memory controller  20 - 1  notifies wireless IC tag  1 - 1  of status signal  2 - 1  representing a temperature, a voltage value, etc. detected from memory chip  22 . 
     FIG. 5  shows an example in which wireless IC tag  1 - 2  is mounted on FAN  2 - 2 . As shown in  FIG. 5 , FAN  2 - 2  has FAN controller  20 - 2  for measuring an operating voltage, a rotational speed, etc. of FAN  2 - 2 . Wireless IC tag  1 - 2  is connected to FAN controller  20 - 2 . In response to a request from wireless IC tag  1 - 2 , FAN controller  20 - 2  notifies wireless IC tag  1 - 2  of status signal  21  representing the measured operating voltage, rotational speed, etc. of FAN  2 - 2 . 
   External wireless module  6  comprises a portable reader such as a handy terminal, for example, and collects status information of component units  2  from wireless IC tags  1  through wireless links  7 . External wireless module  6  is used in the maintenance of the computer system. 
     FIG. 6  shows details of external wireless module  6  in block form. As shown in  FIG. 6 , external wireless module  6  comprises display unit  61 , input unit  62 , transceiver unit  63 , notifying unit  64 , CPU  65 , memory  66 , and antenna  67 . 
   Display unit  61  comprises a liquid crystal display unit, an EL display unit, or the like for displaying status information acquired from wireless IC tags  1 . Input unit  62  issues an instruction to acquire status information to notifying unit  64  based on a key action made by the user. In response to the instruction to acquire status information from input unit  62 , notifying unit  64  generates and sends a READ_LOG packet to each wireless IC tag  1 . The READ_LOG packet includes a program for requesting each wireless IC tag  1  to send status information. Transceiver unit  63  exchanges various signals and data with wireless IC tags  1  through antenna  67 . CPU  65  controls various signals and data in external wireless module  6  and also controls operation of transceiver unit  63  and notifying unit  64 . Acquisition of component configurational information: 
   Operation of the component unit monitoring system according to the first embodiment for acquiring component configurational information will be described below with reference to  FIGS. 7 through 12 . 
     FIG. 9  shows a sequence for detecting component unit  2  that is newly installed in the computer system, and  FIG. 10  shows the formats of wireless packets used in the process of detecting a new component unit. 
   For detecting a new component unit, BMC control circuit  35  of BMC  3  periodically issues a component detection instruction to wireless transmission and reception controller  4  through a physically connected signal line in step S 2  shown in  FIG. 9 . In response to the component detection instruction, wireless transmission and reception controller  4  sends IDENTIFY packet  1000  (see also  FIG. 10 ) to each wireless IC tag  1  through antenna  5  in step S 4 . IDENTIFY packet  1000  includes packet type  1001  and source GUID  1002  representing BMC  3 . 
   In response to IDENTIFY packet  1000 , each wireless IC tag  1  sends EXIST packet  1010  to wireless transmission and reception controller  4  through wireless link  7  in step S 6 . Wireless transmission and reception controller  4  converts EXIST packet  1010  received from wireless IC tag  1  into a format for transmission to BMC  3 , and then sends converted EXIST packet  1010  as an existence notification to detection processor  31  of BMC  3  in step S 8 . EXIST packet  1010  includes packet type  1011 , source GUID  1012 , and information stored in component information area  101  and installation history area  105  of memory map  100  of wireless IC tag  1 , i.e., component information  1013  and installation history  1014 . 
   When detection processor  31  of BMC  3  receives EXIST packet  1010  from each wireless IC tag  1  through wireless transmission and reception controller  4 , detection processor  31  analyzes component information  1013  and installation history  1014  included in EXIST packet  1010 , and compares them with component unit information stored in BMC memory  36 . If there is newly detected component unit  2  or if the computer system finally connected to component unit  2  is different from the computer system which is being connected to BMC  3 , then detection processor  31  determines component unit  2  as a newly detected component unit in step S 10 . 
   When a new component unit is detected, detection processor  31  sends DETECT packet  1020  through wireless transmission and reception controller  4  to wireless IC tag  1  to write an installation history into wireless IC tag  1  in step S 12 . DETECT packet  1020  includes packet type  1021 , source GUID  1022 , target GUID  1023  representing wireless IC tag  1 , detection time  1024  at which the new component unit was detected, system GUID  1025  representing an identifier of the computer system, and system description  1026  representing the name and version information of the computer system. 
   Detection processor  31  also adds new component information to the component configurational information stored in BMC memory  36 . Furthermore, detection processor  31  deletes information of component unit  2  which was not detected as component unit  2  included in the component configurational information, from BMC memory  36  because detection processor  31  regards undetected component unit  2  as being disconnected from the computer system. 
   When tag control circuit  12  of each wireless IC tag  1  receives DETECT packet  1020 , tag control circuit  12  compares target GUID  1023  included in received DETECT packet  1020  with component GUID  111  stored in tag memory  10 . If target GUID  1023  and component GUID  111  are identical to each other, then tag control circuit  12  writes detection time  1024 , system GUID  1025 , and system description  1026  which are included in DETECT packet  1020  into installation history area  105  of memory map  100 . 
     FIG. 11  shows a process performed by BMC  3  for detecting a new component unit. For detecting a new component unit, BMC control circuit  35  of BMC  3  periodically issues a component detection instruction to wireless transmission and reception controller  4  through a physically connected signal line in steps S 102 ,  102  shown in  FIG. 11 . 
   When detection processor  31  receives an existence notification from wireless transmission and reception controller  4  which has received EXIST packet  1010  from each wireless IC tag  1  in step S 106 , detection processor  31  compares the number i of component units  2  connected to the computer system with the number of detected component units from which existence notifications have been received in step S 108 . The initial value of the number i is 0. If i&lt; the number of detected component units (YES in step S 108 ), then detection processor  31  analyzes component information  1013  and installation history  1014  included in EXIST packet  1010  in step S 110 . If system GUID  152  of installation history  1014  is different from the computer system connected to BMC  3 , then component unit  2  corresponding to component information  1013  is judged as a new component unit (YES in step S 112 ). If component unit  2  is not judged as a new component unit (NO in step S 112 ), the number of component units not judged as new component units is added to as a present number to the number i in step S 108 . 
   If component unit  2  is judged as a new component unit, then detection processor  31  issues a new detection instruction for wireless IC tag  1  mounted on component unit  2  corresponding to component information  1013  to wireless transmission and reception controller  4  in step S 114 . At this time, detection processor  31  sends detection time  1024  together with the new detection instruction to wireless transmission and reception controller  4 . After having issued the new detection instruction, detection processor  31  stores component information  1013  and detection time  1024  in BMC memory  36 , thereby updating the component configurational information in step S 116 . 
     FIGS. 12A and 12B  show operation sequences of wireless IC tab  1  for detecting a new component unit.  FIG. 12A  shows a component identifying process for confirming a configuration of the computer system, i.e., whether there is component unit  2  or not. When wireless IC tag  1  receives IDENTIFY packet  1000  from wireless transmission and reception controller  4  through wireless link  7  in step S 202 , power supply  11  operates based on electromagnetic waves from wireless transmission and reception controller  4  and supplies electric energy to the other parts of wireless IC tag  1 . Tag control circuit  12  extracts information stored in component information area  101  and installation history area  105  from tag memory  10  in step S 204 , and generates EXIST packet  1010  including the extracted information in step S 206 . Tag control circuit  12  then sends generated EXIST packet  1010  through wireless link  7  to wireless transmission and reception controller  4  in step S 208 . 
     FIG. 12B  shows a process of detecting a new component unit. When wireless IC tag  1  receives DETECT packet  1020  from wireless transmission and reception controller  4  through wireless link  7  in step S 210 , power supply  11  operates based on electromagnetic waves from wireless transmission and reception controller  4  and supplies electric energy to the other parts of wireless IC tag  1 . Tag control circuit  12  compares component GUID  111  in memory map  100  and target GUID  1023  in DETECT packet  1020  with each other to determine whether the GUIDs are identical to each other or not in step S 212 . If the compared GUIDs are identical to each other, then tag control circuit  12  writes detection time  1024 , system GUID  1025 , and system description  1026  included in DETECT packet  1020  respectively into recognition time  151 , system GUID  152 , and system description  153  in installation history area  105  of memory map  100  in step S 214 . 
   As described above, BMC  3  is capable of managing altogether how component units  2  are installed in the computer system through wireless links  7 . MBC  3  is also capable of controlling each component unit  2  to store its installation history. Even when component unit  2  is removed from the computer system, the user can confirm the installation history of each removed component unit  2 . 
   Since wireless IC tags  1  store component configurational information, it is not necessary to use an NVRAM inherent to the computer system for storing component configurational information. 
   It is also possible to dynamically grasp the configuration of the computer system by accessing the component configurational information of BMC  3  from the program of the computer system. 
   Acquisition of Fault Information: 
   Operation of the component unit monitoring system according to the first embodiment for acquiring fault information will be described below with reference to  FIGS. 7 ,  13  through  16 . 
     FIG. 13  shows a sequence for detecting fault information of component unit  2  connected to the computer system, and  FIG. 14  shows the formats of wireless packets used in the fault information detecting process. 
   For detecting fault information of component unit  2 , BMC control circuit  35  of BMC  3  periodically issues a status acquisition instruction to wireless transmission and reception controller  4  through a physically connected signal line in step S 22  shown in  FIG. 13 . In response to the status acquisition instruction, wireless transmission and reception controller  4  sends GET_STATUS packet  1400  (see also  FIG. 14 ) to each wireless IC tag  1  through antenna  5  in step S 24 . GET_STATUS packet  1400  includes packet type  1401  and source GUID  1402  representing BMC  3 . 
   In response to GET_STATUS packet  1400 , each wireless IC tag  1  sends STATUS packet  1410  to wireless transmission and reception controller  4  through wireless link  7  in step S 26 . Wireless transmission and reception controller  4  converts STATUS packet  1410  received from wireless IC tag  1  into a format for transmission to BMC  3 , and then sends converted STATUS packet  1410  as a status notification to error determining unit  32  of BMC  3  in step S 28 . STATUS packet  1410  includes packet type  1411 , source GUID  1412 , and information stored in component information area  101  and component status area  102  of memory map  100  of wireless IC tag  1 , i.e., component information  1413  and component status  1414 . 
   When BMC control circuit  36  of BMC  3  receives STATUS packet  1410  from each wireless IC tag  1 , BMC control circuit  36  issues a status saving instruction to wireless transmission and reception controller  4  for writing a status history into each wireless IC tag  1  in step S 30 . In response to the status saving instruction, wireless transmission and reception controller  4  sends SAVE_STATUS packet  1420  to each wireless IC tag  1  in step S 32 . SAVE_STATUS packet  1420  includes packet type  1421 , source GUID  1422 , target GUID  1423  representing wireless IC tag  1 , time  1424  at which a fault was detected, and component status  1425  based on received component status  1414 . Target GUID  1423  and component status  1425  are generated based on the values included in GET_STATUS packet  1400 . 
   When tag control circuit  12  of each wireless IC tag  1  receives SAVE_STATUS packet  1420 , tag control circuit  12  compares target GUID  1423  included in received SAVE_STATUS packet  1420  with component GUID  111  in tag memory  10 . If the compared GUIDs are identical to each other, then tag control circuit  12  writes time  1424  and component status  1245  included in SAVE_STATUS packet  1420  respectively into time  131  and status value  132  in status history area  103  in memory map  100 . 
   Error determining unit  32 , which has received STATUS packet  1410  from each wireless IC tag  1  in step S 28 , analyzes component status  1414  contained in received STATUS packet  1410 , and determines whether component unit  2  is suffering a fault, e.g., a reduction in the rotational speed of FAN or a memory ECC (Error Correction Code) error, or not. If error determining unit  32  detects a fault of component unit  2 , then error determining unit  32  issues a fault status saving instruction to wireless transmission and reception controller  4  for writing a fault information history into wireless IC tag  1  that is mounted on faulty wireless IC tag  2  in step S 34 . In response to the fault status saving instruction, wireless transmission and reception controller  4  sends ADD_ERR_LOG packet  1430  to each wireless IC tag  1  in step S 36 . ADD_ERR_LOG packet  1430  includes packet type  1431 , source GUID  1432 , target GUID  1433  representing faulty component unit  2 , time  1434  at which the fault was detected, and faulty type  1435  representing the type of the fault. 
   When tag control circuit  12  of each wireless IC tag  1  receives ADD_ERR_LOG packet  1430 , tag control circuit  12  compares target GUID  1433  included in received ADD_ERR_LOG packet  1430  with component GUID  111  in tag memory  10 . If the compared GUIDs are identical to each other, then tag control circuit  12  writes time  1434 , source GUID  1432 , and fault type  1435  included in ADD_ERR_LOG packet  1430  respectively into time  141 , faulty system GUID  142 , and fault type value  143  in fault information history area  104  in memory map  100 . 
     FIG. 15  shows a process performed by BMC  3  for monitoring fault information. For detecting status information of component unit  2 , BMC control circuit  35  of BMC  3  periodically issues a status acquisition instruction to wireless transmission and reception controller  4  through a physically connected signal line in steps S 302 ,  304  shown in  FIG. 15 . When error determining unit  32  receives a status notification from wireless transmission and reception controller  4  which has received STATUS packet  1410  from each wireless IC tag  1  in step S 306 , error determining unit  32  compares the number i of normal component units with the number of detected component units from which existence notifications have been received in step S 308 . The initial value of the number i is 0. If i&lt;the number of detected component units (YES in step S 308 ), then error determining unit  32  issues a status saving instruction to wireless transmission and reception controller  4  in step S 310 . 
   Error determining unit  32  analyzes component information  1413  and component status  1414  included in STATUS packet  1410  received from wireless IC tag  1 , and determines whether there is a fault or not in step S 312 . Specifically, error determining unit  32  compares component status  1414  with a threshold corresponding to status value  132  obtained from status signal  21  of each component unit  2  and stored in BMC memory  36  to determine whether component unit  2  is suffering a fault or not. Component status  1414  represents, for example, the temperature and voltage of DIMM  2 - 1  or the present rotational speed of FAN  2 - 2 . It is judged that component unit  2  is suffering a fault if component status  1414  is smaller than or greater than the threshold (YES in step S 312 ). If it is judged that component unit  2  is not suffering a fault, then the number of component units  2  that are judged as not suffering a fault is added as the present number of normal component units to the number i (NO in step S 312 ). 
   If error determining unit  32  judges that component unit  2  is suffering a fault based on component information  1413  in STATUS packet  1410 , then error determining unit  32  issues a fault information saving instruction for wireless IC tag  1  mounted on component unit  2  which corresponds to component information  1413  in STATUS packet  1410  to wireless transmission and reception controller  4  in step S 314 . 
     FIGS. 16A through 16C  show operation sequences of wireless IC tab  1  for detecting fault information of component unit  2 .  FIG. 16A  shows a process of wireless IC tag  1  for notifying BMC  3  of the status of component unit  2 . When wireless IC tag  1  receives GET_STATUS packet  1400  from wireless transmission and reception controller  4  through wireless link  7  in step S 402 , power supply  11  operates based on electromagnetic waves from wireless transmission and reception controller  4  and supplies electric energy to the other parts of wireless IC tag  1 . Tag control circuit  12  extracts information stored in component information area  101  and component status area  102  from tag memory  10  in step S 404 , and generates STATUS packet  1410  including the extracted information in step S 406 . Tag control circuit  12  then sends generated STATUS packet  1410  through wireless link  7  to wireless transmission and reception controller  4  in step S 408 . 
     FIG. 16B  shows a process performed by wireless IC tag  1  for saving the status value of component unit  2 . When wireless IC tag  1  receives SAVE_STATUS packet  1420  from wireless transmission and reception controller  4  through wireless link  7  in step S 412 , power supply  11  operates based on electromagnetic waves from wireless transmission and reception controller  4  and supplies electric energy to the other parts of wireless IC tag  1 . Tag control circuit  12  compares component GUID  111  in memory map  100  and target GUID  1422  in SAVE_STATUS packet  1420  with each other. If the compared GUIDs are identical to each other (YES in step S 414 ), then tag control circuit  12  writes detection time  1424  and component status  1424  included in SAVE_STATUS packet  1420  respectively into time  131  and status value  132  in status history area  103  of memory map  100  in step S 416 . 
     FIG. 16C  shows a process performed by wireless IC tag  1  for saving fault information of component unit  2 . When wireless IC tag  1  receives ADD_ERR_LOG packet  1430  from wireless transmission and reception controller  4  through wireless link  7  in step S 422 , power supply  11  operates based on electromagnetic waves from wireless transmission and reception controller  4  and supplies electric energy to the other parts of wireless IC tag  1 . Tag control circuit  12  compares component GUID  111  in memory map  100  and target GUID  1432  in ADD_ERR_LOG packet  1430  with each other. If the compared GUIDs are identical to each other (YES in step S 424 ), then tag control circuit  12  writes detection time  1434  and fault type  1435  included in ADD_ERR_LOG packet  1430  respectively into time  141  and fault type  143  in fault information history area  104  of memory map  100  in step S 426 . Tag control circuit  12  also writes system GUID  152  of the computer system that is presently connected to component unit  2  as faulty system GUID  142  based on the component GUID stored in installation history area. 
   As described above, BMC  3  manages the statuses of component units  2  altogether through wireless links  7 , and controls each component unit  2  to store its fault history. In addition, BMC 3  analyzes the status information which is collected by wireless IC tag  1  to detect a fault of component unit  2 , and controls wireless IC tag  1  to store the detected fault information as a fault history. Therefore, it is easy to analyze the fault histories of individual component units  2 . 
   Acquisition of Status Information by External Wireless Module  6 . 
   Operation of external wireless module  6  of the component unit monitoring system according to the first embodiment for acquiring status information will be described below with reference to  FIGS. 7 ,  17  through  20 .  FIG. 17  shows an operation sequence of external wireless module  6  for acquiring status information, and  FIG. 18  shows the formats of wireless packets used in the status information acquiring process. 
   In response to a status information acquiring instruction from input unit  62 , notifying unit  64  of external wireless module  6  generates READ_LOG packet  1800  (see  FIG. 18 ) including packet type  1801  and source GUID  1802  representing external wireless module  6  as a source, and sends generated READ_LOG packet  1800  to wireless IC tags  1  that are located within the range of wireless links  7  in step S 42  shown in  FIG. 17 . 
   When tag control circuit  12  of each wireless IC tag  1  receives READ_LOG packet  1800 , tag control circuit  12  extracts information stored in component information area  101 , status history area  103 , fault information history area  104 , and installation history area  105  in memory map  100  from tag memory  10 , stores the extracted information respectively into component information area  1813 , status history area  1814 , fault information history area  1815 , and installation history area  1816 , and adds packet type  1811  and source GUID  1812 , thereby generating RETURN_LOG packet  1810 . Tag control circuit  12  sends generated RETURN_LOG packet  1810  through wireless link  7  to external wireless module  6  in step S 44 . 
   When external wireless module  6  receives RETURN_LOG packet  1810  from each wireless IC tag  1 , CPU  6  of external wireless module  6  stores the information included in RETURN_LOG packet  1810  into memory  66 . 
     FIG. 19  shows a process performed by external wireless module  6  for acquiring status information. In response to a status information acquiring instruction from input unit  62 , notifying unit  64  of external wireless module  6  generates READ_LOG packet  1800  (see  FIG. 18 ) including packet type  1801  and source GUID  1802  representing external wireless module  6  as a source, and sends generated READ_LOG packet  1800  to wireless IC tags  1  that are located within the range of wireless links  7  in step S 502  shown in  FIG. 19 . 
   When external wireless module  6  receives RETURN_LOG packet  1810  from each wireless IC tag  1  in step S 504 , CPU  6  of external wireless module  6  refers to source GUID  1812  in RETURN_LOG packet  1810 , and stores component information area  1813 , status history area  1814 , fault information history area  1815 , and installation history area  1816  into memory  66  with respect to each component unit  2  in step S 506 . The component information, the status history, the fault information history, and the installation history which correspond to component unit  2  entered from input unit  62  are selectively displayed on display unit  61 . 
     FIG. 20  shows a process performed by wireless IC tag  1  for acquiring status information. Wireless IC tag  2  that can be connected to external wireless module  6  through wireless link  7  receives READ_LOG packet  1800 , and power supply  11  operates based on electromagnetic waves from external wireless module  6  and supplies electric energy to the other parts of wireless IC tag  1  in step S 602 . Tag control circuit  12  of wireless IC tag  1  which has received READ_LOG packet  1800  extracts information stored in component information area  101 , status history area  103 , fault information history area  104 , and installation history area  105  in memory map  100  from tag memory  10 , stores the extracted information respectively into component information area  1813 , status history area  1814 , fault information history area  1815 , and installation history area  1816 , and adds packet type  1811  and source GUID  1812 , thereby generating RETURN_LOG packet  1810  in step S 606 . Tag control circuit  12  sends generated RETURN_LOG packet  1810  through wireless link  7  to external wireless module  6  in step S 608 . 
   Since an error, such as a FAN error, a memory error, etc. that has occurred in each component unit  2  is written in wireless IC tag  1  attached to component unit  2 , as described above, the fault history of each component unit  2  can easily be analyzed from the information thus stored in wireless IC tag  1 . 
   When the computer system is serviced for maintenance, external wireless module  6  is used to acquire component configurational information and fault information, and also to identify faulty component units regardless of whether the computer system or any faulty component units are turned on or off. 
   Furthermore, as error information is recorded in fault information history area  104  of each wireless IC tag  1 , the error history of each component unit  2  can be traced. 
   2nd Embodiment 
   A component unit monitoring system according to a second embodiment of the present invention will be described below with reference to  FIGS. 7 ,  21  through  26 . 
   The component unit monitoring system according to the second embodiment employs active wireless IC tag  1 ′ having a cell in its power supply  11 ′ as shown in  FIG. 21 . Active wireless IC tag  1 ′ detects a fault of associated component unit  2  on its own, and sends a packet including component information and fault information to BMC  3 ′ (see  FIG. 22 ) through wireless link  7  and wireless transmission and reception controller  4 . 
   The component unit monitoring system according to the second embodiment is of an arrangement which is the same as the component unit monitoring system according to the first embodiment. 
   Active wireless IC tag  1 ′ operates on electric energy supplied from the cell in power supply  11 ′ for communicating with wireless transmission and reception controller  4  and external wireless module  6 . Wireless transmission and reception controller  4  and external wireless module  6  operate on the multiple access principles to communicate with all wireless IC tags  1  in the computer system. BMC  3 ′ and external wireless module  6  are capable of selectively controlling wireless IC tags  1 ′ to obtain status information therefrom by inserting GUIDs of wireless IC tags  1 ′ into data transmitted to wireless IC tags  1 ′. 
     FIG. 21  shows in block form wireless IC tag  1 ′ according to the second embodiment. As shown in  FIG. 21 , wireless IC tag  1 ′ has tag memory  10 , power supply  11 ′, tag control circuit  12 ′, transceiver unit  13 , tag antenna  14 , and error determining unit  15  which are connected to each other by a bus. Tag memory  10  has memory map  100  and stores a threshold which is received from BMC  3 ′ through wireless transmission and reception controller  4  and used for determining an error. Power supply  11 ′ has a cell as described above and supplies electric energy to the other parts of wireless IC tag  1 ′. 
   Tag control circuit  12 ′ controls signals and data in wireless IC tag  1 ′. Tag control circuit  12  also periodically issues a signal for requesting status signal  21  from component control device  20  to acquire status information of component unit  2 . Transceiver unit  13  controls signals and data that are input and output through tag antenna  14 , and also controls status signal  21  supplied from component control device  20 . Transceiver unit  13  also modulates and demodulates signals and data that are input and output through tag antenna  14 . 
   Error determining unit  15  analyzes status signal  21  received from component control device  20  using the threshold stored in tag memory  10  to determine whether component unit  2  is suffering a fault or not. 
     FIG. 22  shows in block form BMC  3 ′ according to the second embodiment. As shown in  FIG. 22 , BMC  3 ′ has notifying unit  33 ′, transceiver unit  34 , BMC control circuit  35 , and BMC memory  36  which are connected to each other by a communication bus. Transceiver unit  34  is connected to wireless transmission and reception controller  4  through motherboard  2 - 4 . Transceiver unit  34  controls wireless transmission and reception controller  4  to communicate with wireless IC tags  1 ′ and external wireless module  6  through antenna  5 . BMC  3 ′ is controlled by a program such as an OS of the computer system through motherboard  2 - 4 . 
   BMC control circuit  35  controls signals and data in BMC  3 ′ and also controls operation of notifying unit  33 . Transceiver unit  34  controls various signals and data that are input and output between wireless transmission and reception controller  4  and system program  8 . 
   Wireless IC tags  1 ′ are mounted on component units  2  as shown in  FIGS. 4 and 5 , and acquire status signal  21 . 
   External wireless module  6  is of an arrangement which is identical to the arrangement of external wireless module  6  according to the first embodiment. 
   Acquisition of Fault Information: 
   Operation of the component unit monitoring system according to the first embodiment for acquiring fault information will be described below with reference to  FIGS. 7 ,  23  through  26 . 
     FIG. 23  shows a sequence for detecting fault information of component unit  2  connected to the computer system, and  FIG. 24  shows the formats of wireless packets used in the fault information detecting process. 
   BMC control circuit  35  of BMC  3 ′ issues a threshold setting instruction for setting a threshold used to determine a fault of each component unit  2  in each wireless IC tag  1 ′, to wireless transmission and reception controller  4  in step S 52  shown in  FIG. 23 . In response to the threshold setting instruction from BMC control circuit  35 , wireless transmission and reception controller  4  sends SET_THRESHOLD packet  2200  (see  FIG. 24 ) to wireless IC tags  1 ′ that are located within the wireless communication range of the computer system in step S 54 . SET_THRESHOLD packet  2200  includes packet type  2201 , source GUID  2202  representing BMC  3 ′, target GUID  2203  representing wireless IC tag  1 ′ mounted on component unit  2 , and threshold  2204  read from BMC memory  36 . 
   When error determining unit  15  of wireless IC tag  1 ′ receives SET_THRESHOLD packet  2200 , error determining unit  15  saves threshold  2204  in received SET_THRESHOLD packet  2200  into tag memory  10 . Error determining unit  15  also compares saved threshold  2204  with status value  121  stored in tag memory  10  to determine whether component unit  2  is suffering a fault or not. If it is judged that component unit  2  is suffering a fault in step S 55 , then error determining unit  15  sends NOTIFY packet  2210  including packet type  2211 , source GUID  2212 , and fault type  2213  representing the type of the fault through wireless link  7  to wireless transmission and reception controller  4  in step S 56 . 
   When wireless transmission and reception controller  4  receives NOTIFY packet  2210 , wireless transmission and reception controller  4  sends received NOTIFY packet  2210  as a fault notification to BMC  3 ′ in step S 58 . In response to the fault notification, BMC  3 ′ issues a fault information saving instruction for saving fault information to wireless transmission and reception controller  4  in step S 60 . In response to the fault information saving instruction, wireless transmission and reception controller  4  sends an ADD_ERR_LOG packet to wireless IC tag  1 ′ in step S 62 . When wireless IC tag  1 ′ receives the ADD_ERR_LOG packet, wireless IC tag  1 ′ saves analyzed fault information acquired from component unit  2  in association with a fault detection time in tag memory  10 . 
     FIG. 25  shows a process performed by BMC  3 ′ for monitoring fault information according to the second embodiment. When BMC  3 ′ issues a threshold setting instruction for writing a threshold used to determine a fault of each component unit  2  in each wireless IC tag  1 ′, to wireless transmission and reception controller  4 , wireless transmission and reception controller  4  sends SET_THRESHOLD packet  2200  to each wireless IC tag  1 ′ in step S 702 . BMC  3 ′ waits for a fault notification from wireless IC tags  1 ′ that are being monitored, i.e., that are located within the range of wireless links  7  in the same computer system, in step S 704 . When BMC  3 ′ receives NOTIFY packet  2210  from wireless IC tag  1 ′ in step S 706 , BMC  3 ′ issues a fault information saving instruction to wireless IC tag  1 ′ represented by a target GUID which is indicated by source GUID  2212  included in NOTIFY packet  2210  in step S 708 . After having issued the fault information saving instruction, BMC  3 ′ waits for a fault notification again. 
     FIG. 26  shows a fault information notifying process performed by wireless IC tag  1 ′ according to the second embodiment. Error determining unit  15  of wireless IC tag  1 ′ receives SET_THRESHOLD packet  2200  in step S 802  and stores the threshold in SET_THRESHOLD packet  2200  into tag memory  10  in step S 804 . Tag control circuit  12 ′ periodically receives status signal  21  from component control device  20 , and sends the acquired status value to error determining unit  15 . Error determining unit  15  compares the status value from tag control circuit  12 ′ with the threshold in tag memory  10 . If the status value exceeds the threshold in tag memory  160 , then error determining unit  15  judges that component unit  2  is suffering an error, i.e., a fault (YES in step S 806 ). When error determining unit  15  judges that component unit  2  is suffering an error, error determining unit  15  generates NOTIFY packet  2210  including fault type  2213  in step S 808 , and sends generated NOTIFY packet  2210  through wireless link  7  to BMC  3 ′ in step S 810 . As described above, error determining unit  15  periodically analyzes the status value acquired from component unit  2 , and stores fault information which is obtained as a result of the analysis in association with the detection time into tag memory  10  according to a fault information saving instruction from BMC  3 ′. 
   According to the second embodiment, as described above, when each active wireless IC tag  1 ′ detects a fault on its own, active wireless IC tag  1 ′ transmits fault information to BMC  3 ′ and stores the fault information as a fault history. Consequently, the component unit monitoring system according to the second embodiment is not required to perform the polling process that is necessary in the component unit monitoring system according to the first embodiment. 
   As with the component unit monitoring system according to the first embodiment, the component unit monitoring system according to the second embodiment allows external wireless module  6  to acquire fault information from each wireless IC tag  1 ′ through wireless link  7 . Therefore, it is possible to grasp whether component unit  2  is suffering a fault or not regardless of whether the computer system is turned on or off. 
   3rd Embodiment 
   A component unit monitoring system according to a third embodiment of the present invention is similar to either one of the component unit monitoring systems according to the first and second embodiments except that the component unit monitoring system employs single wireless IC tag  1  mounted on component unit  2  and connected to the computer system, and single wireless IC tag  1  stores a fault information history. The fault information history is recorded in the same manner as with the component unit monitoring systems according to the first and second embodiments. Therefore, a faulty component can be identified and analyzed regardless of whether the computer system is turned on or off. 
   4th Embodiment 
   A component unit monitoring system according to a fourth embodiment of the present invention is similar to either one of the component unit monitoring systems according to the first, second, and third embodiments except that it has wireless transmission and reception controller  4 ′ connected in common to BMCs  3  of a plurality of computer systems, instead of wireless transmission and reception controller  4 , and operates in the same manner as with the component unit monitoring systems according to the first, second, and third embodiments. According to the fourth embodiment, wireless transmission and reception controllers are not installed in association with respective servers, e.g., blade servers, accommodated in a rack mount system, but single wireless transmission and reception controller  4 ′ is disposed in the rack mount system. Single wireless transmission and reception controller  4 ′ is capable of detecting all wireless IC tags that are involved. The component unit monitoring system with the single wireless transmission and reception controller is relatively simple in structure and can monitor component units at a reduced cost. 
   The present invention is not limited to the details of the illustrated embodiments, but many changes and modifications may be made therein without departing from the scope of the invention. For example, according to the first and second embodiments, the data of the fields of response packets (EXIST, STATUS) from wireless IC tags are generated by extracting some values stored in memory map  100  of tag memory  10 . However, the data of the fields of response packets may be generated by extracting all the values stored in memory map  100  for simplifying the processing in the wireless IC tags. 
   In component unit monitoring systems according to the first through fourth embodiments, the information stored in the wireless IC tags and communication packets that are exchanged through wireless links  7  may be encrypted against unauthorized access from third parties. 
   The accumulated running time of each of the component units may be stored in the corresponding wireless IC tag. The timing for replacement of the component unit combined with the wireless IC tag may then be judged based on the accumulated running time stored in the wireless IC tag. 
   The accumulated running time thus stored is particularly useful for managing consumable products such as FANs, HDDs, etc. 
   Furthermore, information representing the shipment date and sold date of each of the component units may also be stored in the corresponding wireless IC tag. Based on the stored information representing the shipment date and sold date, it can be determined whether the component unit is still under guarantee or not. The information thus stored is particularly useful for managing products having certain guarantee periods. 
   In the above embodiments, component units to be monitored are included in a computer system. However, component units to be monitored may be external devices such as portable USB memories. If an external device is to be monitored, then a wireless IC tag is mounted on the external product for managing information of the external device. 
   If a component unit monitoring system monitors external devices, then an installation history and a file transfer history may be stored in a wireless IC tag mounted on each of the external devices, and the component unit monitoring system may have a function to inhibit external devices free of wireless IC tags from being used. The component unit monitoring system thus arranged may be combined with a security check system in a building for checking unauthorized attempts to take classified data out of the building based on the information stored in wireless IC tags mounted on external devices. 
   While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.