Patent Document

BACKGROUND 
     1. Field of the Invention 
     This invention relates to graphics. In particular, the invention relates to graphics port interface. 
     2. Background of the Invention 
     A typical graphics display system may have a number of graphics capabilities. An integrated chipset may have internal graphics controller and interface to an external graphic device via a graphics port. Depending on system requirements and platform, a user may select whether the internal graphics controller or the external graphic device is used. To provide flexibility for board manufacturers or Original Equipment Manufacturers (OEM&#39;s) in designing graphics-based systems, it is desirable to have an efficient mechanism to select the desired graphics capability. However, since the signal definitions for the internal graphics controller are usually different than those of the interface graphics port for external devices, it is a design challenge to provide this selection mechanism. 
     One technique for the selection of the desired graphics capability is to provide two sets of guidelines: one set for the internal graphics controller and another set for the external device. This technique creates complexity in board designs and incur additional software overhead for configuration and initialization. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the present invention will become apparent from the following detailed description of the present invention in which: 
     FIG. 1 is a diagram illustrating a system in which one embodiment of the invention can be practiced. 
     FIG. 2A is a diagram illustrating an integrated chipset located in the chipset space  125  shown in FIG. 1 according to one embodiment of the invention. 
     FIG. 2B is a diagram illustrating separate chipsets located in the chipset space  125  shown in FIG. 1 according to one embodiment of the invention. 
     FIG. 3A is a diagram illustrating mapping of data and command signals for the DVO and AGP modes on the interface port according to one embodiment of the invention. 
     FIG. 3B is a diagram illustrating mapping of other signals for the DVO and AGP modes on the interface port according to one embodiment of the invention. 
     FIG. 4A is a diagram illustrating pin assignment on side A of the interface port for the DVO and AGP modes according to one embodiment of the invention. 
     FIG. 4B is a diagram illustrating pin assignment on side B of the interface port for the DVO and AGP modes according to one embodiment of the invention. 
     FIG. 5 is a flowchart illustrating a process to configure the graphics mode according to one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the present invention. In other instances, well-known electrical structures and circuits are shown in block diagram form in order not to obscure the present invention. For examples, although the description of the invention is directed to the digital video output (DVO) and accelerated graphics port (AGP) graphics modes, the invention can be practiced for other graphics modes having similar characteristics. It is also noted that the invention may be described as a process, which is usually depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. Although a flowchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be re-arranged. A process is terminated when its operations are completed. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination corresponds to a return of the function to the calling function or the main function. 
     FIG. 1 is a diagram illustrating a computer system  100  in which one embodiment of the invention can be practiced. The computer system  100  includes a processor  110 , a host bus  120 , a chipset space  125 , an interface port  130 , an on-board digital video output (DVO) device  140 , an external DVO device  142 , an encoder  144 , a television set  146 , an on-board accelerated graphics port (AGP) device  150 , an AGP connector  152 , an external AGP device  154 , an AGP digital display (ADD) card  156 , a system memory  160 , a mass storage device  170 , and input/output devices  180   1  to  180   K . Note that not all of these devices are present in a typical system. In some cases, the presence of a device precludes another device. For example, if an on-board device is present, an external similar device is not needed. 
     The processor  110  represents a central processing unit of any type of architecture, such as embedded processors, micro-controllers, digital signal processors, superscalar computers, vector processors, single instruction multiple data (SIMD) computers, complex instruction set computers (CISC), reduced instruction set computers (RISC), very long instruction word (VLIW), or hybrid architecture. In one embodiment, the processor  110  is compatible with the Intel Architecture (IA) processor, such as the IA-32 and the IA-64. The host bus  120  provides interface signals to allow the processor  110  to communicate with other processors or devices, e.g., the memory controller hub (MCH)  130 . The host bus  120  may support a uni-processor or multiprocessor configuration. The host bus  120  may be parallel, sequential, pipelined, asynchronous, synchronous, or any combination thereof. 
     The chipset space  125  is a space to receive one or more chipsets. The chipset(s) to be plugged into the chipset space  125  may be an integrated chipset or chipsets with separate functionalities. The integrated chipset may have functionalities equivalent to a memory controller, a graphics controller, and an input/output (I/O) controller. The separate chipsets may include a memory controller chipset and an I/O controller chipset. The invention provides a mechanism to maintain compatibility with various configurations for the chipset space  125 . 
     The interface port  130  provides connection pins to interface to a number of devices. The interface port  130  includes multiplexed pins to support at least two graphics modes. In one embodiment, these graphics mode includes a DVO mode and an AGP mode. The DVO mode may include a digital visual interface (DVI) which supports transition minimized differential signal (TMDS) or low voltage differential signaling (LVDS) devices. By having a common interface port for both graphics signals used in the two graphics modes, a significant saving in hardware and software can be realized. In addition, the single interface port  130  provides a single set of guidelines which facilitates the design of add-on devices or cards. Alternatively, the interface port  130  may provide a set of guidelines and other devices or cards may follow another set of guidelines. 
     The on-board and external TMDS/LVDS devices  140  and  142  are graphic devices that interface to the DVO signaling from the interface port  130 . The on-board TMDS/LVDS device  140  is located on the motherboard containing the processor  110  while the external TMDS/LVDS device  142  is an add-on card to be plugged into a slot having interface to the interface port  130 . The TMDS/LVDS devices  140  and  142  drive a flat panel display or a digital display monitor through a TMDS/LVDS transmitter. The encoder  144  encodes the digital pixel data generated by the graphics controller from the chipset at the chipset space  125  into a usable video signal. The television set  146  receives the video signal from the encoder  144  in a suitable format such as National Television System Committee (NTSC), phase alternation by line (PAL), or sequential technique and memory storage (SECAM) and displays the graphics information. 
     The on-board AGP device  150  is a graphic device that is compatible to the AGP standard such as the AGP Version 2.0 Standard (published in “Accelerated Graphics Port Interface Specification” Revision 2.0 by Intel Corporation, May 4, 1998). The on-board AGP device  150  interfaces directly to the interface port  130  and is located on the motherboard that contains the processor  110 . The AGP connector  152  is a connector that supports the AGP standard (e.g., version 2.0). The external AGP device  154  is an add-on AGP-compatible graphics device located externally to the motherboard. The ADD card  156  is a graphics device that interfaces to the AGP connector  152  and is compatible to the DVO mode. The ADD card  156  may support a 12-bit or 24-bit, 1.5 v signaling compliant DVO device. 
     The system memory  160  stores system code and data. The system memory  160  is typically implemented with dynamic random access memory (DRAM) or static random access memory (SRAM). The system memory may include an operating system, device drivers, and software to initialize or configure the various graphics modes. The system memory  140  may also include other programs or data, which are not shown depending on the various embodiments of the invention. 
     The mass storage device  170  stores archive information such as code, programs, files, data, applications, and operating systems. The mass storage device  170  may include compact disk (CD) ROM  172 , floppy diskettes  174 , and hard drive  176 , and any other magnetic or optic storage devices. The mass storage device  170  provides a mechanism to read machine-readable media. 
     The I/O devices  180   1  to  180   K  may include any I/O devices to perform I/O functions. Examples of I/O devices  180   1  to  180   K  include controllers for input devices (e.g., keyboard, mouse, trackball, pointing device), media cards (e.g., audio, video, graphics), network cards, and any other peripheral controllers. 
     FIG. 2A is a diagram illustrating an integrated chipset  205  located in the chipset space  125  shown in FIG. 1 according to one embodiment of the invention. The chipset space  125  is occupied by the integrated chipset  205 . The integrated chipset  205  is a graphics and memory controller hub (GMCH). 
     The integrated chipset  205  includes a memory controller  210 , an internal graphics controller  220 , a hub interface  230 , and an optional Input/Output controller hub (ICH)  240 . 
     The memory controller  210  controls the system memory  140  (FIG.  1 ). The internal graphics controller  220  is a graphics engine that can perform a number of graphics operations. In one embodiment, the internal graphics controller  220  provides shading, filtering, clipping, and three-dimensional (3-D) transformations. The internal graphics controller  220  operates in parallel or works in conjunction with the AGP controller. The internal graphics controller  220  provides a display interface  222  and a DVO interface  224 . The display interface  222  generates synchronization signals such as vertical sync and horizontal sync, red green blue (RGB) color information, and other video signals to drive an analog video display monitor. The DVO interface  224  generates DVO data and clock signals for DVO devices, and the display control signals (e.g., M 12 C) which may be used to drive flat panel display. The AGP interface  226  generates AGP-compatible signals for use in the AGP mode. The AGP interface  226  provides an upgrade path for graphics capability if the internal graphics controller  220  is not sufficient. The hub interface  230  provides interface signals to the ICH  240 . The ICH  240  may be integrated within the chipset  205  or may be located externally to the chipset  205 . The ICH  240  has a number of functionalities that are designed to support I/O functions. The ICH  240  may include a number of interface and I/O functions such as PCI bus interface, processor interface, interrupt controller, direct memory access (DMA) controller, power management logic, timer, universal serial bus (USB) interface, mass storage interface, low pin count (LPC) interface, etc. The ICH  240  includes a mass storage controller to control the mass storage device  170  (FIG.  1 ). It is contemplated that the system  100  may also include peripheral buses such as Peripheral Component Interconnect (PCI), accelerated graphics port (AGP), Industry Standard Architecture (ISA) bus, and Universal Serial Bus (USB), etc. 
     In many systems that use the integrated chipset  205 , the AGP connector  152  (FIG. 1) is linked to the AGP interface  226  to provide a graphics upgrade path. When the AGP connector  152  is not populated with an external AGP device (e.g., the external AGP card  154  in FIG.  1 ), it is possible to make use of the multiplexed digital display channels via the ADD card  156 . The ADD card  156  is plugged into the AGP connector  152  but has digital display devices that use the multiplexed digital display channels. Alternatively, DVO devices may be soldered down on the motherboard containing the processor  110 . 
     FIG. 2B is a diagram illustrating separate chipsets located in the chipset space  125  shown in FIG. 1 according to one embodiment of the invention. The chipset space  125  is occupied by a memory controller hub  250  and the ICH  240 . 
     The MCH  250  includes a memory controller  252  and an AGP interface  255 . The memory controller  252  performs similar functions as the memory controller  210  shown in FIG.  2 A. The AGP interface  255  provides AGP-compatible signals for AGP modes. The MCH  250  does not have an internal graphics controller that supports the DVO mode. The ICH  240  is described above. 
     Since the MCH  250  does not have an internal graphics controller, it can only support the AGP mode. The interface port  130  can be used for either DVO or AGP modes. The interface port  130  can be used with the MCH  250  when the system is configured to operate in a suitable mode. 
     Within an AGP-only interface, the signals are divided into several categories: 1x timing domain and 2x/4x timing domain. There are three sets of signals acting as sub-groups within the 2x/4x domain. A DVO interface has several similar characteristics when compared to an AGP interface, especially an AGP interface that runs in the 4x mode. The interface port  130  provides an optimized method to multiplex the DVO signals on an AGP interface. This method focuses on the similarities of the two graphics signals and masks off the differences. 
     FIG. 3A is a diagram illustrating mapping of data and command signals for the DVO and AGP modes on the interface port according to one embodiment of the invention. 
     The DVO mode supports two DVO ports, DVOB and DVOC, multiplexed on the AGP interface. Each of the ports can be configured as a 12-bit TV-out port or a 12-bit digital-out port. The two ports can be combined to enable 24-bit digital out to support high-resolution digital display. The DVOB data signals include DVOB_D 0  to DVOB_D 11  and the DVOB command signals include DVOB_Hsync, DVOB_Vsync, DVOB_Blank, DVOBC_Clk_Int, and DVOB_Fld/Stl. The DVOC data signals include DVOC_D 0  to DVOC_D 11  and the DVOC command signals include DVOC_Hsync, DVOC_Vsync, DVOC_Blank, DVOBC_Clk_Int, and DVOC_Fld/Stl. These signals are mapped or multiplexed on the AGP data and command signals. Since the data and command signals on the DVO and the AGP have similar characteristics, multiplexing the data and command signals of the DVO mode into the data and command signals of the AGP mode leads to the same design guidelines, simplifying board design work. 
     The mapping of the DVOB signals to the AGP signals is as follows: 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 DVOB_D0 
                 to 
                 AD3 
               
               
                   
                 DVOB_D1 
                 to 
                 AD2 
               
               
                   
                 DVOB_D2 
                 to 
                 AD5 
               
               
                   
                 DVOB_D3 
                 to 
                 AD4 
               
               
                   
                 DVOB_D4 
                 to 
                 AD7 
               
               
                   
                 DVOB_D5 
                 to 
                 AD6 
               
               
                   
                 DVOB_D6 
                 to 
                 AD8 
               
               
                   
                 DVOB_D7 
                 to 
                 C/BE#0 
               
               
                   
                 DVOB_D8 
                 to 
                 AD10 
               
               
                   
                 DVOB_D9 
                 to 
                 AD9 
               
               
                   
                 DVOB_D10 
                 to 
                 AD12 
               
               
                   
                 DVOB_D11 
                 to 
                 AD11 
               
               
                   
                 DVOB_Hsync 
                 to 
                 AD0 
               
               
                   
                 DVOB_Vsync 
                 to 
                 AD1 
               
               
                   
                 DVOB_Blank 
                 to 
                 C/BE#1 
               
               
                   
                 DVOBC_Clk_Int 
                 to 
                 AD13 
               
               
                   
                 DVOB_Fld/Stl 
                 to 
                 AD14 
               
               
                   
                   
               
             
          
         
       
     
     The mapping of the DVOC signals to the AGP signals is as follows: 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 DVOC_D0 
                 to 
                 AD19 
               
               
                   
                 DVOC_D1 
                 to 
                 AD20 
               
               
                   
                 DVOC_D2 
                 to 
                 AD21 
               
               
                   
                 DVOC_D3 
                 to 
                 AD22 
               
               
                   
                 DVOC_D4 
                 to 
                 AD23 
               
               
                   
                 DVOC_D5 
                 to 
                 C/BE#2 
               
               
                   
                 DVOC_D6 
                 to 
                 AD25 
               
               
                   
                 DVOC_D7 
                 to 
                 AD24 
               
               
                   
                 DVOC_D8 
                 to 
                 AD27 
               
               
                   
                 DVOC_D9 
                 to 
                 AD26 
               
               
                   
                 DVOC_D10 
                 to 
                 AD29 
               
               
                   
                 DVOC_D11 
                 to 
                 AD28 
               
               
                   
                 DVOC_Hsync 
                 to 
                 AD17 
               
               
                   
                 DVOC_Vsync 
                 to 
                 AD16 
               
               
                   
                 DVOC_Blank 
                 to 
                 AD18 
               
               
                   
                 DVOBC_Clk_Int 
                 to 
                 AD30 
               
               
                   
                 DVOC_Fld/Stl 
                 to 
                 AD31 
               
               
                   
                   
               
             
          
         
       
     
     FIG. 3B is a diagram illustrating mapping of other signals for the DVO and AGP modes and miscellaneous signals on the interface port according to one embodiment of the invention. 
     The other signals for the DVO mode include a detector signal (ADD_Detect), DVO clock signals (DVOB_CLK, DVOB_CLK#, DVOC_CLK, and DVOC_CLK#), display control signals (MI 2 C_data, MI 2 C_Clk, MDDC_data, MDDC_Clk, MX_data, and MX_Clk), and ADD configuration signals (ADD_ID 0  to ADD_ID 7 ). The miscellaneous signals include a type detect (TYPEDET) signal and a reset (RST#) signals. 
     The mapping of these signals to the AGP signals is as follows: 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 ADD_Detect 
                 to 
                 PAR 
               
               
                   
                 DVOB_CLK 
                 to 
                 AD_STB0 
               
               
                   
                 DVOB_CLK# 
                 to 
                 AD_STB0# 
               
               
                   
                 DVOC_CLK 
                 to 
                 AD_STB1 
               
               
                   
                 DVOC_CLK# 
                 to 
                 AD_STB1# 
               
               
                   
                 TYPEDET 
                 to 
                 TYPEDET# 
               
               
                   
                 RST# 
                 to 
                 RST# 
               
               
                   
                 MI2C_data 
                 to 
                 DEVSEL# 
               
               
                   
                 MI2C_Clk 
                 to 
                 IRDY# 
               
               
                   
                 MDDC_data 
                 to 
                 FRAME# 
               
               
                   
                 MDDC_Clk 
                 to 
                 TRDY# 
               
               
                   
                 MX_data 
                 to 
                 STOP# 
               
               
                   
                 MX_Clk 
                 to 
                 AD15 
               
               
                   
                 ADD_ID0 
                 to 
                 SBA0 
               
               
                   
                 ADD_ID1 
                 to 
                 SBA1 
               
               
                   
                 ADD_ID2 
                 to 
                 SBA2 
               
               
                   
                 ADD_ID3 
                 to 
                 SBA3 
               
               
                   
                 ADD_ID4 
                 to 
                 SBA4 
               
               
                   
                 ADD_ID5 
                 to 
                 SBA5 
               
               
                   
                 ADD_ID6 
                 to 
                 SBA6 
               
               
                   
                 ADD_ID7 
                 to 
                 SBA7 
               
               
                   
                   
               
             
          
         
       
     
     The ADD_Detect signal is used to identify that the ADD card  156  (FIG. 1) is used instead of the AGP card  154 . The PAR signal of the AGP mode has fairly loose requirement according to the AGP Specification 2.0. The system  100  using the integrated chipset  205  does not violate the AGP specification if the PAR signal is at a HIGH logic level at reset. One way to do this is to use a pull-up resistor at the PAR signal. In one embodiment, this pull-up resistor has a value of approximately 8.2KΩ. To indicate that an ADD card is used, the ADD card pulls this signal LOW. When this occurs, the integrated chipset  205  disables the PCI configuration register #1 (host to AGP bridge). This causes the integrated chipset to behave as if it had no AGP interface and will not attempt to initialize the AGP mode. A system that does not use the integrated chipset  205  and uses a MCH only will ignore the ADD card  156  according to the AGP Specification 2.0. 
     The configuration signals ADD_ID 0  to ADD_ID 7  are strapped to high or low depending on the configuration of the ADD card  156 . These signals are mapped or multiplexed onto the AGP SBA 0  to SBA 7 , respectively. Since the SBA signals are meant to be input only to the MCH the AGP mode, these signals are not driven. Therefore, no initialization lockup will occur if the ADD card  156  is used in a system that does not use the integrated chipset  205 . 
     The display control signals (e.g., the MI 2 C_data, MI 2 C_Clk, MDDC_data, MDDC_Clk, MX_data, and MX_Clk signals) are low frequency signals, typically operating at lower than 400 Khz. Therefore, mapping these signals to the low frequency signals of the AGP mode maintains the same design guidelines for both graphics modes. The miscellaneous signals (e.g., TYPEDET, RST#) are for compatibility with AGP specification. 
     FIG. 4A is a diagram illustrating the pin assignment on side A of the interface port for the DVO and AGP modes according to one embodiment of the invention. 
     FIG. 4B is a diagram illustrating the pin assignment on side B of the interface port for the DVO and AGP modes according to one embodiment of the invention. 
     FIG. 5 is a flowchart illustrating a process  500  to configure the graphics mode according to one embodiment of the invention. 
     Upon START, the process  500  initializes and configures the appropriate graphics mode (Block  510 ). Then, the process  500  determines if the ADD_Detect signal is enabled (Block  520 ). A LOW level on the ADD_Detect signal indicates that the ADD card is enabled via the AGP. If ADD_Detect is enabled, the process  500  initializes the AGP mode and is then terminated. Otherwise, the process  500  disables the host processor to AGP bridge (Block  540 ). Next, the process  500  initializes the DVO mode (Block  550 ) and is then terminated. 
     While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications of the illustrative embodiments, as well as other embodiments of the invention, which are apparent to persons skilled in the art to which the invention pertains are deemed to lie within the spirit and scope of the invention.

Technology Category: g