Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1998-10-19
2001-10-23
Auve, Glenn A. (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C345S520000, C703S024000
Reexamination Certificate
active
06308237
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to a method and system to be utilized in data processing systems. In particular, the present invention relates to a method and system to be utilized in data processing systems wherein a faster device communicates with a slower device, such as the non-limiting example of data processing systems wherein the Accelerated Graphics Port (AGP) interface standard is utilized.
2. Description of the Related Art
Data processing systems are systems that manipulate, process, and store data and are notorious within the art. Personal computer systems, and their associated subsystems, constitute well known species of data processing systems. Personal computer systems in general and IBM compatible personal computer systems in particular have attained widespread use for providing computer power to many segments of today's modern society. A personal computer system can usually be defined as a desk top, floor standing, or portable microcomputer that includes a system unit including but not limited to a system processor and associated volatile and non-volatile memory, a display device, a keyboard, one or more diskette drives, one or more fixed disk storage devices, and one or more data buses for communications between devices. One of the distinguishing characteristics of these systems is the use of a system board to electrically connect these components together. These personal computer systems are information handling systems which are designed primarily to give independent computing power to a single user (or a relatively small group of users in the case of personal computers which serve as computer server systems) and are inexpensively priced for purchase by individuals or small businesses.
A computer system or data-processing system typically includes a system bus. Attached to the system bus are various devices that may communicate locally with each other over the system bus. For example, a typical computer system includes a system bus to which a central processing unit (CPU) is attached and over which the CPU communicates directly with a system memory that is also attached to the system bus.
In addition, the computer system may include a peripheral bus for connecting certain highly integrated peripheral components to the CPU. One such peripheral bus is known as the Peripheral Component Interconnect (PCI) bus. Under the PCI bus standard, peripheral components can directly connect to a PCI bus without the need for glue logic. Thus, PCI is designed to provide a bus standard on which high-performance peripheral devices, such as graphics devices and hard disk drives, can be coupled to the CPU, thereby permitting these high-performance peripheral devices to avoid the general access latency and the band-width constraints that would have occurred if these peripheral devices were connected to a low speed peripheral bus. Details on the PCI local bus standard can be obtained under the PCI Bus Specification, Revision 2.1, from the PCI Special Interest Group, which is hereby incorporated by reference in its entirety.
Relatively recently, techniques for rendering three-dimensional (3D) continuous-animation graphics have been implemented within PCs which, as will be explained below, have exposed limitations in the originally high performance of the PCI bus. The AGP interface standard has been developed to both (1) reduce the load on the PCI bus systems, and (2) extend the capabilities of systems to include the ability to provide 3D continuous-animation graphics with a level of quality previously found only on high-end computer workstations. The AGP interface standard is defined by the following document: Intel Corporation,
Accelerated Graphics Port Interface Specification
, Revision 1.0 (Jul. 31, 1996), which is hereby incorporated by reference in its entirety.
The AGP interface standard is specifically targeted to improve the efficiency of 3D continuous-animation graphics applications which utilize a technique know in the art as “texturing.” Consequently, as background for understanding the data processing systems utilizing the AGP interface standard, it is helpful to have a brief overview of the data processing needs of 3D continuous animation graphics applications which utilize texturing, how they degrade the performance of PCI local bus systems, and how the AGP interface standard remedy this degradation of performance.
The display device of a computing system displays data in two-dimensions (2D). In order to create a 3D continuous animation graphical display, it is first necessary to create an object such that when the object is presented on the 2D display device, the object will be perceived by a human viewer as a 3D object. There are two basic ways in which this can be done. The first way is to use color and shading techniques to trick the human visual system into perceiving 3D objects on the 2D display device (essentially the same technique used by human artists when creating what appear to be 3D landscapes consisting of trees, rocks, streams, etc., on 2D canvases). This is a very powerful technique and creates superior 3D realism. The second way is to use mutually perpendicular lines (e.g., the well-known x, y, z coordinate system) to create geometric objects which will be interpreted by the human visual system as denoting 3D (essentially the same technique used by human architects to create the illusion of 3D in perspective view architectural drawings). However, the 3D illusion created by the use of mutually perpendicular lines is generally perceived to be inferior to that produced by the coloring and shading techniques.
Subsequent to creating a 3D object, the object must be animated. Animation is the creation of the illusion of continuous motion by the rapid sequential presentation of discrete images, or frames, upon the 2D display device. Animated 3D computer graphics are generated by taking advantage of a well know physiological property of the human visual system which is that if a person is shown a sequence of 15 discrete snapshots of a continuous motion, where each snapshot was taken in {fraction (1/15)} second intervals, within one second, the brain will integrate the sequence together such that the person will “see,” or perceive, continuous motion. However, due to person-to-person variations in physiology, it has been found empirically that a presentation of 20 images per second is generally the minimum rate at which the majority of people will perceive continuous motion without flicker, with 30 images per second tending to be the accepted as the optimal presentation speed.
The difficulty with 3D continuous animation computer graphics is that while the color and shading techniques (which are typically accomplished via bit-mapped images) produce superior 3D realism, such techniques are not easy for a computer to translate through geometric space for the creation of continuously varying sequential images necessary to produce the animation effect. On the other hand, the geometric shapes produced via the use of mutually perpendicular lines allow for easy computer manipulation in three dimensions, which allows the creation of sequential images necessary to produce the animation effect, but such geometric shapes result in inferior 3D realism. Recent 3D continuous-animation computer graphics techniques take advantage of both of the foregoing noted 3D techniques via the use of a middle ground approach known in the art “texturing.”
In the use of texturing, the gross, overall structures of an object are denoted by a 3D geometric shape which is used to do geometric translation in three space, while the finer details of each side of the 3D object are denoted by bit mapped images (known in the art as “textures”) which accomplish the color and shading techniques. Each time a new image of an object is needed for animation, the geometric representation is pulled from computer memory into a CPU, and the appropriate translations calculated. Thereafter, the translated geometric representation is cached and
Qureshi Qadeer A
Strongin Geoffrey S.
Advanced Micro Devices , Inc.
Auve Glenn A.
Skjerven Morrill & MacPherson LLP
Terrile Stephen A.
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