Abstract:
An accelerated graphic port (AGP) system uses several control signals to allow an AGP graphic card to enter into negotiation with a motherboard. These control signals can drive the motherboard to provide AGP operating voltage (VCCQ) and providing a first reference voltage for the motherboard according to the AGP operating voltage. On the other hand, the motherboard will provide a second reference voltage to the AGP graphic card according to the determination of whether or not the AGP graphic card is an AGP8X card. Therefore the universal AGP connector of the present invention can enable all kinds of AGP graphic cards to be coupled to the motherboard, and can prompt the motherboard to meet with all the AGP system specifications and support all kinds of AGP graphic cards.

Description:
FIELD OF THE INVENTION 
     The present invention is related to an accelerated graphic port (AGP) system and the method for operating the same, and more particularly to an AGP system that supports all kinds of AGP modes and meets with all the AGP system specifications and the operating method thereof. 
     BACKGROUND OF THE INVENTION 
     A typical computer system generally includes several bus systems as the interface for the peripheral devices and the host processor. In the computer system today, the PCI (peripheral component interconnect) bus is treated as a main system I/O bus for enabling the peripheral devices to proceed to data transfers with the host computer. Nonetheless, in some specific applications, such as video and 3-D graphics applications, it requires even greater throughput than PCI bus can provide. Because of the need for the increased bandwidth between the host processor and the video subsystem, the traffic on the PCI bus is becoming heavier and heavier, and the hard disk, video graphic adapter card (VGA card) and the peripheral devices are all competing for the same I/O bandwidth. In order to overcome the eventual saturation of the I/O bandwidth of the PCI bus, a new interface has been pioneered by Intel Corporation which is designed specifically for the video subsystem. It is commonly referred to as accelerated graphic port (AGP). The AGP enables the audio, video or graphic cards to efficiently make use of system memory. In particular, AGP provides a high-throughput interconnected channel for the peripheral devices such as audio, video and graphic cards to access the system memory. 
     With the mushroom development of the AGP technology, a variety of AGP operating modes have been addressed up to now. As indicated in FIG. 1, the differences among a variety of current AGP operating modes are listed. The configuration settings of signaling, signal swing, reference voltage, AGP operating voltage (VCCQ) and AGP slot selection for different AGP modes can be seen from FIG. 1 to get a better understanding to the characteristics of AGP systems. It is to be known from FIG. 1 that if 3.3V keyed AGP slot is selected, it can support AGP mode only; if 1.5V keyed AGP slot is selected, it can support AGP 4 X and AGP 8 X modes only, if universal AGP slot is selected, it can support AGP and AGP 4 x modes only. Accordingly, if it is intended to plug an AGP graphic card into a motherboard of a host computer through an AGP slot, the AGP slot can not be compatible with all kinds of AGP specifications due to the restrictions of the AGP operating modes for which the AGP slot can support. 
     As a result, in order to enable the antiquated AGP 1 X, AGP 2 X and AGP 4 X graphic cards to be compatible with the AGP 8 X-enabled motherboard, a universal AGP system is essential for supporting all the existent AGP system specifications, including AGP mode (AGP 1 X and  2 X signaling), AGP 4 X mode (AGP 1 X,  2 X and  4 X signaling) and AGP 8 X mode (AGP 8 X signaling only), so as to eliminate the problems associated with the compatibility among different AGP system specifications. 
     SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide an AGP system which is configured so as to support all kinds of the AGP system specifications. 
     Another object of the present invention is to provide an AGP connector which can provide a communication channel for all kinds of AGP graphic cards to communicate with the motherboard of a host computer. 
     In accordance with the AGP system of the present invention, five control signals transmitted at the interface of an AGP graphic card and a motherboard are used to allow the AGP graphic card to enter into negotiation with the motherboard. These five control signals are transmitted between the AGP graphic card and the motherboard through five pins of the AGP connector, respectively. A first control signal is provided by the AGP graphic card to the motherboard for driving the voltage-switching circuit of the motherboard to generate an AGP operating voltage according to a state of the first control signal. A second control signal is provided by the system core logic of the motherboard for notifying the AGP graphic card whether or not the motherboard supports AGP 8 X operating mode. A third control signal is provided by the AGP graphic card to the system core logic of the motherboard for notifying the motherboard whether or not the AGP graphic card is an AGP 8 X graphic card. A fourth control signal is transmitted from the AGP graphic card to the motherboard for providing a first AGP reference voltage according to the AGP operating mode of the AGP graphic card for the motherboard. A fifth control signal is transmitted from the motherboard to the AGP graphic card for providing a second AGP reference voltage according to the determination of whether or not the AGP graphic card is an AGP 8 X graphic card for the AGP graphic card. 
     It is worthy to note that the motherboard can selectively generate an AGP operating voltage according to the AGP operating mode indicated by the first control signal. The resultant AGP operating voltage is used to select a first AGP reference voltage corresponding to the AGP operating mode for the motherboard. On the other hand, the motherboard can generate a second AGP reference voltage corresponding to the AGP operating mode According to the determination of whether or not the AGP graphic card is an AGP 8 X graphic card to the AGP graphic card. 
     Now the foregoing and other features and advantages in connection with the present invention will become apparent through the following descriptions with reference to the accompanying drawings, wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a tabulation listing the differences among a variety of AGP modes; 
     FIG. 2 is a tabulation explicating the five control signals transmitted at the interface of the AGP graphic card and the motherboard; 
     FIG. 3 shows the functional block diagram of the universal AGP system according to a preferred embodiment of the present invention; and 
     FIG. 4 is a tabulation listing the differences between the prior AGP 8 X system and the universal AGP system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is presented with a universal AGP system for permitting all kinds of AGP graphic cards (AGP 1 X, AGP 2 X, AGP 4 X and AGP 8 X) to be coupled with a motherboard, and prompting the motherboard to support all kinds of AGP graphic cards. 
     For achieving the objectives of providing an AGP system that can meet with all kinds of AGP specifications and support all the AGP operating modes, the present invention makes use of five control signals transmitted at the interface of AGP graphic card and the motherboard through five pins of the AGP slot respectively to determine the AGP operating mode. With regard to other control signals transmitted at the interface of the AGP graphic card and the motherboard, they are of little interest to the present invention, and we are not inclined to give a detailed discussion herein. 
     In relation to the five pins of the AGP slot and the aforementioned five control signals transmitted thereon at the interface of AGP graphic card and the motherboard for determining the AGP operating mode, it will become apparent by way of the following descriptions and the tabulation of FIG.  2  and the functional block diagram of FIG.  3 . 
     1. The first control signal TYPEDET# is an asynchronous signal transmitted from the AGP graphic card through Pin No. A 2  of the AGP slot to the motherboard. The TYPEDET# signal is used to determine the AGP operating voltage (VCCQ) for the motherboard. If the TYPEDET# signal is open, the AGP operating voltage for the motherboard is 3.3V; if TYPEDET# signal is short to ground, the AGP operating voltage for the motherboard is 1.5V. 
     2. The second control signal MB_AGP 8 X_DET# is an asynchronous signal provided by the system core logic of the motherboard and transmitted through Pin No. A 11  of the AGP slot to the AGP graphic card. The MB_AGP 8 X_DET# signal is used to determine that the motherboard is AGP  8  X enabled or not. If the MB_AGP 8 X_DET# signal is open, it indicates that the motherboard does not support AGP 8 X signaling and protocol, so that the motherboard is not AGP 8 X enabled; If the MB_AGP 8 X_DET# signal is short to ground, it indicates that the motherboard supports AGP 8 X signaling and protocol, so that the motherboard is AGP 8 X enabled. 
     3. The third control signal GC_AGP 8 X_DET# is an asynchronous signal provided by the AGP graphic card and transmitted through Pin No. A 3  of the AGP slot to the motherboard. The GC_AGP 8 X_DET# signal is used to determine that the AGP graphic card is an AGP 8 X graphic card or not. If the GC_AGP 8 X_DET# signal is open, it indicates that the AGP graphic card does not support AGP 8 X signaling and protocol, so that the AGP graphic card is not an AGP 8 X graphic card; If the GC_AGP 8 X_DET# signal is short to ground, it indicates that the AGP graphic card supports AGP 8 X signaling and protocol, so that the AGP graphic card is an AGP 8 X graphic card. 
     4. The fourth control signal V ref     —   GC is an asynchronous signal representing the AGP reference voltage provided by the AGP graphic card based on the AGP operating mode to the motherboard, and transmitted through Pin No. A 66  of the AGP slot. If the V ref     —   GC signal is open, it indicates that the AGP operating mode is AGP mode; if the V ref     —   GC signal is 0.5VCCQ, it indicate that the AGP operating mode is AGP 4 X; if the V ref     —   GC signal is 0.35VCCQ, it indicates that the AGP operating mode is AGP 8 X. 
     5. The fifth control signal V ref     —   CG is an asynchronous signal representing the AGP reference voltage provided by the motherboard based on the AGP operating mode to the AGP graphic card, and transmitted through Pin No. B 66  of the AGP slot. If the V ref     —   CG signal is open, it indicates that the AGP operating mode is AGP mode; if the V ref     —   CG signal is 0.5VCCQ, it indicate that the AGP operating mode is AGP 4 X; if the V ref     —   CG signal is 0.35VCCQ, it indicates that the AGP operating mode is AGP 8 X. 
     The following embodiment will fully illustrate how the universal AGP system of the present invention can support all kinds of AGP system specifications and operating modes in accordance with the above discussions and with references to FIG. 1, FIG.  2  and FIG.  3 . 
     FIG. 3 show a functional block diagram of the universal AGP system according to a preferred embodiment of the present invention. In FIG. 3, the universal AGP system according to a preferred embodiment of the present invention includes an AGP graphic card  11 , an AGP universal connector  12  and a motherboard  10 . The AGP graphic card  11  includes a graphic controller  111  which serves as an AGP master. The motherboard  10  includes a voltage-switching circuit or a voltage regulator  101 , a system core logic  102  including a second multiplexer  1021 , an on-board reference voltage divider  103  including a first multiplexer  1031 . The universal AGP connector  12  as shown in FIG. 3 only displays the pins related to the five control signals as discussed above, but other pins of the universal AGP connector  12  are not displayed for the sake of simplification. However, those of skill in the art will clearly recognize the signal processing and operation algorithm of the universal AGP system of the present invention in virtue of the following descriptions. 
     In FIG. 3, the voltage-switching circuit (voltage regulator)  101  of the motherboard  10  receives the first control signal TYPEDET# and generates an AGP operating power (VCCQ) in response to the state of the first control signal TYPEDET#. Besides, the AGP operating power (VCCQ) generated by the voltage-switching circuit  101  will be introduced to the second multiplexer  1021  of the system core logic  102  for generating an actual reference voltage for use by the system core logic  102 . The practical operations of the voltage-switching circuit  101  are described as follows. If the first control signal TYPEDET# is open, the TYPEDET# signal received by the voltage-switching circuit  101  will be at a high state to drive the voltage-switching circuit  101  to generate an AGP operating voltage (VCCQ) of 3.3V, which indicates the AGP operating mode is AGP mode (with signaling  1 X and  2 X supported), and the AGP graphic card is an AGP 1 X or AGP 2 X graphic card. Adversely, if TYPEDET# signal is short to ground, the TYPEDET# signal received by the voltage-switching circuit  101  will be at a low state to drive the voltage-switching circuit  101  to generate a VCCQ of 1.5V, which indicates the AGP operating mode is AGP 4 X (with signaling  1 X,  2 X and  4 X supported) or AGP 8 X mode (with signaling  8 X supported), and the AGP graphic card is an AGP 4 X or AGP 8 X graphic card. As to whether the AGP graphic card  11  is an AGP 4 X or AGP 8 X graphic card, it depends on the signaling level of the third control signal GC_AGP 8 X_DET#. 
     The second control signal MB_AGP 8 X_DET# is a control signal indicating that the system core logic  102  notifies the graphic controller  111  whether or not the motherboard  10  supports AGP 8 X signaling and protocol. If the MB_AGP 8 X_DET# signal is open, it indicates that the motherboard  10  does not support AGP 8 X signaling and protocol, so that the motherboard  10  is not AGP 8 X enabled. On the other hand, if the MB_AGP 8 X_DET# signal is short to ground, it indicates that the motherboard supports AGP 8 X signaling and protocols, so that the motherboard is AGP 8 X enabled. It is noted that if the motherboard  10  is not AGP 8 X enabled (that is, the MB_AGP 8 X_DET# signal is open), the AGP graphic card  11  has to be adjusted to the operating modes that are supported by the motherboard  10  (for example, AGP 4 X, AGP 2 X and AGP 1 X) in advance, and then enters into negotiation with the motherboard  10  by way of the AGP operating voltage. The system core logic  102  includes a second multiplexer  1021  which receives a 0.4VCCQ voltage signal and a voltage signal represented by the fourth control signal V ref     —   GC, and takes the AGP operating voltage (VCCQ) generated by the voltage-switching circuit  101  as its selection signal to generate an appropriate AGP reference voltage for the system core logic  102 . If the AGP graphic card  11  is an AGP 1 X or AGP 2 X graphic card, because the V ref     —   GC signal is open and VCCQ is 3.3V, the second multiplexer  1021  will output a voltage signal of 0.4VCCQ as the AGP reference voltage for the system core logic  102 . And it can be understood that the reference voltage of 0.4VCCQ indicates that the AGP operating mode is AGP mode from the tabulation of FIG.  1 . In addition, if the AGP graphic card  11  is an AGP 4 X graphic card, because the V ref     —   GC signal is 0.5VCCQ and VCCQ is 1.5V, the second multiplexer  1021  will select 0.5VCCQ (the V ref     —   GC signal) as its output and the AGP reference voltage for the system core logic  102 . Furthermore, if the AGP graphic card  11  is an AGP  8  X graphic card, because the V ref     —   GC signal is 0.35VCCQ and VCCQ is 1.5V, the second multiplexer  1021  will select 0.35VCCQ (the V ref     —   GC signal) as its output and the AGP reference voltage for the system core logic  102 . In this manner, the AGP graphic card  11  can be coupled to the motherboard  10  through the universal AGP connector of the present invention regardless of the type of the AGP graphic card  11 , and the motherboard  10  can support all kinds of AGP graphic cards. 
     The third control signal GC_AGP 8 X_DET# is fed to the system core logic  102  for notifying the motherboard  10  whether or not the graphic controller  111  supports AGP 8 X signaling and protocol. If the GC_AGP 8 X_DET# signal is open, it indicates that the graphic controller  111  does not support AGP 8 X signaling and protocol, so that the AGP graphic card  11  is not an AGP 8 X graphic card. On the contrary, if the GC_AGP 8 X_DET# signal is short to ground, it indicates that the graphic controller  111  supports AGP 8 X signaling and protocol, so that the AGP graphic card  11  is an AGP 8 X graphic card. The GC_AGP 8 X_DET# will respectively feed to the system core logic  102  to notify the system core logic  102  whether or not the AGP graphic card  11  is an AGP 8 X graphic card, and to an on-board reference voltage divider  103  to determine the AGP reference voltage for the graphic controller  111 . The on-board reference voltage divider  103  includes a first multiplexer  1031  which receives a voltage signal of 0.5VCCQ and a voltage signal of 0.35VCCQ, and takes the third control signal GC_AGP 8 X_DET# as its selection signal. When the third control signal GC_AGP 8 X_DET# is open (the signal state is high), it indicate that the AGP graphic card  11  is not an AGP 8 X graphic card, and the first multiplexer  1031  will select 0.5VCCQ as its output and the AGP reference voltage for the graphic controller  111 . On the contrary, when the third control signal GC_AGP 8 X_DET# is short to ground (the signal state is low), it indicate the AGP graphic card  11  is an AGP 8 X graphic card, the first multiplexer  1031  will select 0.35VCCQ as its output and the AGP reference voltage for the graphic controller  111 . 
     It should be noted that if the AGP graphic card  11  is an AGP 1 X or AGP 2 X graphic card, though the third control signal GC_AGP 8 X_DET# is open, the AGP reference voltage for use by the AGP graphic card  11  (0.4VCCQ) is generated internally by the AGP graphic card  11  itself, but is not necessary to be provided by the motherboard  10 . In other words, when the AGP graphic card  11  is an AGP 1 X or AGP 2 X graphic card, the voltage signal of V ref     —   CG outputted from the first multiplexer  1031  belongs to a don&#39;t care signal. It is obvious from the above interpretations that if the AGP graphic card  11  is an AGP 1 X or AGP 2 X graphic card, the motherboard  10  is not necessary to provide an AGP reference voltage to the AGP graphic card  11 ; If the AGP graphic card  11  is an AGP 4 X or AGP 8 X graphic card, the motherboard  10  will first determine whether the AGP graphic card  11  is an AGP 8 X graphic card (the determination of whether or not the AGP graphic card  11  is an AGP 8 X graphic card is carried out by the GC_AGP  8  X_DET# signal), and then provides an appropriate AGP reference voltage to the AGP graphic card  11 . Hence the motherboard  10  can provide an appropriate AGP reference voltage to the AGP graphic card  11  regardless of the type of the AGP graphic card  11 . 
     FIG. 4 graphically illustrates the differences between the AGP system of the present invention and the prior AGP 8 X system. It is to be known from FIG. 4 that the universal AGP connector of the present invention can mate with all kinds of AGP graphic cards, but the universal AGP connector for the prior AGP 8 X system is the same with a 1.5V keyed slot, and can match with AGP 4 X or AGP 8 X graphic card only. Further, comparing the AGP system of present invention with the prior AGP 8 X system in terms of the AGP operating voltage (VCCQ), it is found that the AGP system of the present invention can provide a VCCQ of 3.3V or 1.5V as desired. However, the prior AGP 8 X system can provide a VCCQ of 3.3V only. Apparently, the AGP system of the present invention can use the abovementioned five control signals to get backward compatibility with the AGP 1 X, AGP 2 X and AGP 4 X graphic cards, so as to achieve the purpose of supporting all kinds of AGP system specifications. 
     It is to be noted that when the AGP graphic card  11  transmits the V ref     —   GC signal to the motherboard  10 , the motherboard  10  can transmit the V ref     —   CG signal to the AGP graphic card  11  simultaneously. In addition, if the AGP graphic card  11  supports the AGP 8 X operating mode but the motherboard does not support, the AGP graphic card  11  has to be adjusted its operating mode to the AGP operating modes that the motherboard  10  can support (AGP 4 X, AGP 2 X or AGP 1 X), and then enters into negotiation with the motherboard  10  by the control signals TYPEDET# and so on. 
     Although the present invention has been described and illustrated in detail, it is to be clearly understood that the same is by the way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.