Patent Publication Number: US-2005132118-A1

Title: System and a method for adapting an AGP-interfaced apparatus to a PCI controller

Description:
BACKGROUND OF THE INVENTION  
      (1) Field of the Invention  
      The present invention relates to a system for adapting an accelerated graphic port (AGP) interfaced apparatus to a periphery component interconnect (PCI) controller and a method for adapting the same, and more particularly relates to a system that adapts an AGP-interfaced apparatus to a PCI controller by connecting an AGP connector to a PCI controller directly and a method for adapting the same.  
      (2) Description of Related Art  
      A computer system typically includes a mother board with a system bus formed thereon as a basic component. Various devices such as a central processing unit (CPU), a chipset, and memories adapted on the mother board are communicated with each other. The chipset plays a role of ruling signal and data transmission on the system bus and periphery buses. The choice of particular chipset is according to the CPU. In addition, there should be various connectors attending with such periphery buses for connecting periphery components such as displaying cards, hard disks, soft disks, CDROMs, etc.  
      Referring to  FIG. 1 , there is a prior art mother board with a Southbridge (SB)  200  and a Northbridge (NB)  100 . The NB  100  deals with data and signal transmission between a CPU  120 , a main memory  140 , and an AGP connector  160 . The NB  100  also communicates with the SB  200  by using a particular transmission protocol. The SB  200  has a PCI controller, an IDE controller, a USB controller, and other specific controllers for controlling various periphery components  220 ,  240 ,  260 ,  280 , so that the SB  200  is capable of dealing with input/output (I/O) signals from the periphery components  220 ,  240 ,  260 ,  280 . Furthermore, the SB  200  also transmits interrupt requests from the periphery components  220 ,  240 ,  260 ,  280  to the NB  100  to ask the CPU  120  to arrange a proper operation schedule to deal with the periphery components  220 ,  240 ,  260 ,  280 .  
      An AGP interface standard is developed to reduce the load of the PCI interface because of the need of a huge datastream resulted by texture mapping technique solely for 3D image, and it is based on a set of performance extensions and enhancements to the PCI interface. Referring to Table 1, the distinctions of the AGP interface and the PCI interface, such as the dimension of the connectors and the way of data transmission, are described.  
                       TABLE 1                       Interface   AGP   PCI                  Speed   32 Bits   32 Bits       Frequency   66 Mhz   33/66 Mhz       Number of contacts   132 (dual layer 4×), 124   120 (single layer)           (dual layer 8×)       Data Transmission   Pipelined   Non-pipelined       Address/Data transmission   Address/Data   Address/Data           de-multiplexing   multiplexing       Data-stream Speed   1066 MB/S (4×)   133 MB/S           2133 MB/S (8×)   (33 MHz)                  
 
      The specifications and advantages of the AGP interface are: 1) pipelined memory read and write operations, 2) de-multiplexing of address and data on the AGP bus by use of sideband signals, and 3) data transfer rates of 133 MHz for data throughput in excess of 500 MB/S. The AGP specification is neither meant to replace nor diminish full use of the PCI interface in the computer standard.  
      As mentioned, the AGP interface provides an independent and additional high-speed bus other than the PCI interface, through which the AGP interface is led to be one of the mainstreams in displaying card industry. However, some chipset manufacturers, such as Intel, still provide low-ended NB chips, such as 854 GVs, which don&#39;t support the AGP interface. Therefore, some old fashion PCBs that don&#39;t support the AGP interface, or some new designed PCBs that include NB chips but don&#39;t support the AGP interface are still alive, but encounter a circumstance of no compatible displaying card of PCI interface available. Moreover, in a need to assemble a computer system with two displaying cards to support two displaying equipments, a traditional PCB comprising only one AGP connector still needs a second displaying card of PCI interface. Yet, such a PCB still meets the problem of no compatible PCI displaying card available.  
      As shown in  FIG. 2 , a prior art AGP/PCI adapter  20  acts as a bridge between an AGP interfaced apparatus  30  and a PCI connector  12 . A lower side of the AGP/PCI adapter  20  has PCI fingers  22 , and an upper side has an AGP connector  24 . The PCI fingers  22  are inserted into the PCI connector  12  on the mother board  10 , and the AGP connector  24  at the upper side accepts the AGP interfaced apparatus  30  with AGP fingers.  
      As shown in  FIG. 3A , when the AGP interfaced apparatus  30  is accepted by an AGP connector  14  formed on the mother board  10 , in/out ports of the AGP interfaced apparatus  30  definitely match the openings on a back plate of the PC housing  40 , and also the AGP interfaced apparatus  30  can be screw-fixed thereto.  
      Whereas, as shown in  FIG. 3B , when the AGP/PCI adapter  20  is inserted between a PCI connector  12  on the mother board  10  and the AGP interfaced apparatus  30 , the AGP interfaced apparatus  30  must be moved upward, and thus the thread holes  32  on the AGP interfaced apparatus  30  cannot match the respective thread hole  42  anymore on the PC housing  40 . It is easy to see in  FIG. 3B  that an adapting and fixing problem is inevitable.  
     SUMMARY OF THE INVENTION  
      It is therefore an object of the present invention to provide a computer system adapting an AGP interfaced apparatus to a PCI connector formed on a mother board.  
      It is a further object of the present invention to provide a mother board, which is able to adapt an AGP interface to a PCI controller so as to solve the compatible problem of the PCI displaying card.  
      It is another object of the present invention to provide an adapting method for solving the mismatch problem between the AGP interfaced apparatus and the PC housing when an AGP/PCI adapter is used.  
      The mother board of the present invention comprises a PCI controller and an AGP connector. The PCI controller can be an independent IC or situated in an NB or a SB. Part of the electric contacts of the AGP connector connect to the PCI controller for address and data transmission. Furthermore, the AGP connector connects to a power source for accessing a driving voltage with a voltage level in reference to that of a PCI connector.  
      Among all the electric contacts of the AGP connector, AGP specified contacts, which presents the distinction between the AGP interface and the PCI interface, such as a strobe, a status signal, a sideband signal, a read buffer full signal, and a write buffer full signal, are all opened.  
      The method of adopting an AGP interfaced apparatus to a PCI controller comprises the steps of: 1) providing a mother board with a PCI controller formed thereon; 2) forming an AGP connector with contacts divided into a first group and a second group on the mother board, wherein the contacts of the second group are AGP specified contacts; 3) connecting the contacts of the first group to the PCI controller, and having the contacts of the second group contacts remain opened.  
      Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which:  
       FIG. 1  depicts a schematic view of a typical mother board with a chipset including a Southbridge (SB) and a Northbridge (NB) thereon;  
       FIG. 2  depicts a schematic view of adapting an AGP apparatus to a PCI interface by using a traditional AGP/PCI adapter;  
       FIG. 3A  depicts a schematic view of plugging an AGP displaying card into an AGP connector with the displaying card screw-fixed to the PC housing;  
       FIG. 3B  depicts a schematic view of plugging an AGP displaying card into a PCI connector by using a traditional AGP/PCI adapter;  
       FIG. 4A  depicts a schematic view of a preferred embodiment of the mother board in accordance with the present invention for adapting an AGP apparatus to a PCI controller;  
       FIG. 4B  depicts a schematic view of another embodiment of the mother board in accordance with the present invention for adapting an AGP apparatus to a PCI controller;  
       FIG. 4C  depicts a schematic view of the other embodiment of the mother board in accordance with the present invention for adapting an AGP apparatus to a PCI controller;  
       FIG. 5  shows a description of contacts in a conventional AGP connector;  
       FIG. 6  shows a description of contacts in a conventional PCI connector;  
       FIG. 7  shows a description of contacts in an AGP connector in accordance with the present invention;  
       FIG. 8  depicts a flowchart of a preferred embodiment for adapting an AGP interfaced apparatus to a PCI controller in accordance with the present invention;  
       FIG. 9  depicts a schematic view of a preferred embodiment of a computer system in accordance with the present invention; 
    
    
      Table 1 presents the difference between a typical AGP interface and a typical PCI interface;  
      Table 2 describes the contacts of an AGP connector in accordance with the present invention, which shows characteristics of the AGP transmission; and  
      Table 3 describes the opened contacts in the AGP connector in accordance with the present invention.  
     DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 4A  shows a preferred embodiment of a mother board for adapting an AGP interfaced apparatus to a PCI controller, in which the mother board comprises a central processing unit (CPU)  120 , a Northbridge (NB)  100 , a Southbridge (SB)  200 , an AGP connector  230 , and at least a PCI connector  220  (three shown in the embodiment). The NB  100  deals with data and signal transmission between the CPU  120  and main memory  140 , and it also communicates with the SB  200  through a PCI bus (not shown in the figure). A PCI controller  210  is provided in the SB  200  for forming connections with both the AGP connector  230  and the PCI connectors  220 .  
      The PCI controller  210  may be provided in the NB  100  or in an independent IC other than SB  200  or NB  100  if necessary. As an independent IC, the PCI controller  210 , which forms a connection with the AGP connector  230 , may communicate with the SB  200  directly as shown in  FIG. 4B , or communicate with the NB  100  directly as shown in  FIG. 4C .  
      By comparing the electric contacts within a conventional AGP connector shown in  FIG. 5  and that within a conventional PCI connector shown in  FIG. 6 , it is noted that every contact within the PCI connector has a respective contact within the AGP connector. Moreover, the AGP connector has twenty more contacts for presenting AGP character, which are described in groups in Table 2.  
               TABLE 2                       AGP Sideband Address Signal                                        PIPE#   Pipelined Read: providing an AGP characterized pipelined           data transmission.       SBA[7:0]   Sideband Address: providing connections for transmission           Address and Command.                 AGP Data-stream Controlling Signal                     RBF#   Read Buffer Full: announcing AGP controller that the           plugged AGP displaying card is full and no data is           accessible.       WBF#   Write Buffer Full: announcing the plugged AGP displaying           card that the AGP controller is full and no data is           accessible.                 AGP Status Signal                     ST[2:0]   Status: monitoring an operation status of the AGP           displaying card.                 AGP Timing Signals                     ADSTB_A   AD Bus Strobe A: providing a timing control for the           D/A buses.       ADSTB_B   AD Bus Strobe B: providing a timing control for the D/A           buses also.       SBSTB   Sideband Strobe: providing a timing control for the           Sideband Signal bus.                  
 
      As shown in Table 2, the electric contacts for presenting AGP character is separated into Sideband Addressing Signals, Data-stream Control Signals, Status Signals, and Timing Signals. The Sideband Addressing Signals are used to present multi-pipelined transmission and sideband addressing. The Timing Signals are used to control the timing of data transmission in replacement of a timer within a PCI interface. The Data-stream Control Signals and the Status Signals are used to inform the user of the operation status of the AGP interfaced apparatus, such as an AGP interfaced displaying card.  
      In addition, no matter an AGP connector or a PCI connector is used, a power supply for providing a driving voltage is definitely demanded. Basically, a typical AGP connector is integrated with a 1.5 V power supply or a 3.3 V power supply, while a typical PCI connector is integrated with a 3.3 V power supply or a 5 V power supply.  
      In order to adapt the AGP connector to the PCI controller without sacrificing the normal operation of the PCI controller, only part of the electric contacts (named the first group contacts) within the AGP connector of  FIG. 7  are connected to the PCI controller through a typical PCI bus. The rest contacts within the AGP connector (named the second group contacts) are opened, in which these contacts as described in Table. 3 includes: 1) Address Strobe contacts, 2) Status Signal contacts, 3) Sideband Signal contacts, 4) Read Buffer Full Signal contacts, and 5) Write Buffer Full Signal contacts.  
                           TABLE 3                                   Representation   Position of Contacts                          OVRCNT#   B1           USB   A4, B4           RESERVED   A22, B22, A24, A44, B44, A42           PIPE#   A12, B14           SBA[7:0]   A15, B15, A17, B17, A20, B20, A21, B21           RBF#   B12           WBF#   A14           ST[2:0]   A10, B10, B11           ADSTB   A32, B32, A59, B59           SBSTB   A18, B18                      
 
      The contacts in Table 3 is divided into two groups, originally opened contacts, such as OVRCNT#, USB, and RESERVED contacts, and AGP specified contacts, such as Address Strobe contacts, Status Signal contacts, Sideband Signal contacts, Read Buffer Full Signal contacts, and Write Buffer Full Signal contacts.  
       FIG. 8  shows a flowchart of a preferred embodiment for adapting an AGP interfaced apparatus to a PCI controller in accordance with the present invention. A mother board is provided with a PCI controller and an AGP connector. The AGP connector has a plurality of electric contacts divided into a first group and an AGP specified second group. In step  300 , the first group contacts are connected to the PCI control through a PCI bus. Afterward, in step  320 , the AGP specified second group contacts are opened. Thereafter, in step  340 , because the AGP connector in accordance with the present invention is connected with a PCI controller, the AGP connector must be integrated with a PCI standard power supply for attaining a PCI standard driving voltage level.  
      It is noted that the electric contacts described in Table 2 are useless with respect to the PCI controller. But even connecting the electric contacts described in Table 2 to the NB, because the A/D contacts of the AGP connector in accordance with the present invention connect to the PCI controller, the NB cannot dominate the operation of the AGP connector.  
       FIG. 9  is a preferred embodiment of a computer system for adapting an AGP interfaced apparatus to a PCI controller. The NB  100  deals with data and signal transmission between a CPU  120 , a main memory  140 , and a first AGP connector  232 , and it also communicates with the SB  200  through a bus. The PCI controller  210  is provided in the SB  200  and forms connections with a second AGP connector  234  and three PCI connectors  220 .  
      As shown, the computer system is provided with two AGP connectors  232  and  234 , and it is capable to adapt two AGP interfaced displaying cards  250 , wherein one displaying card is communicated with the NB  100  and is operated through an AGP interface, while the other displaying card is communicated with the SB  200  and is operated through a PCI interface. Thus, the mentioned computer system is able to support two monitors by using two AGP displaying cards  250  simultaneously.  
      In reference to the method for adapting an AGP interfaced apparatus to a PCI controller by using an AGP/PCI adapter  20  of  FIG. 3B . The method in accordance with the present invention has the following advantages:  
      1. In  FIGS. 4A, 4B , and  4 C, the mother board in accordance with the present invention has an AGP connector  230 , which connects to the PCI controller  210 , for accepting an AGP interfaced apparatus, such as AGP displaying card. Thus, the AGP/PCI adaptor  20  is not needed and the cost of the computer system can be reduced.  
      2. As mentioned, because the AGP/PCI adapter  20  is not needed in the present invention, the signal transmission distance between the AGP interfaced apparatus and the PCI controller  210  can be reduced so as to lower the signal bias rate in signal transmission and thus the operational speed can be substantially increased.  
      3. The AGP connector formed on the mother board for accepting the AGP interfaced apparatus in accordance with the present invention can act as a typical AGP connector. Thus, the AGP interfaced apparatus plugged into the AGP connector can be properly screw-fixed to the PC housing and the problem resulted from the usage of AGP/PCI adaptor  20  shown in  FIG. 3B  can be avoided.  
      With the example and explanations above, the features and spirits of the invention will be hopefully well described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made when retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.