Computer graphics processing and selective visual display system – Computer graphics display memory system – Memory allocation
Reexamination Certificate
2000-12-13
2003-11-11
Tung, Kee M. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics display memory system
Memory allocation
C345S531000, C711S170000
Reexamination Certificate
active
06646646
ABSTRACT:
TECHNICAL FIELD
The present invention is related generally to the field of computer graphics, and more particularly, to a memory system and method for use in a computer graphics processing system.
BACKGROUND OF THE INVENTION
Graphics processing systems are typically memory intensive systems, requiring a significant amount of memory to render graphics images with sufficient speed and quality. The memory appears as a contiguous memory space, but is often physically separated into various levels. For example, a graphics processing system usually includes a portion of embedded memory integrated with the other circuitry of the graphics processing system to form a single device, as well as a portion of external memory that is not integrated onto the device, but is located locally and dedicated for graphics processing. At a third level, system memory belonging to a host computer in which the graphics processing system is located may be accessed by the graphics processing system.
Generally, embedded memory included in a graphics processing system allows data to be provided to processing circuits, such as the graphics processor, the pixel engine, and the like, with low access times. The proximity of the embedded memory to the graphics processor and its dedicated purpose of storing data related to the processing of graphics information enable data to be moved throughout the graphics processing system quickly. Thus, the processing elements of the graphics processing system may retrieve, process, and provide graphics data quickly and efficiently, increasing the processing throughput. The embedded memory is used by the graphics processing system for a variety of purposes. For example, the embedded memory is often allocated for z-buffering purposes to store the depth values of graphics primitives in a three-dimensional image. Another use is as a pixel buffer to store the color values of pixels that are used for processing, or that will be rendered. Still another use is as a texture buffer to store texture map data where texture mapping is to be applied during rendering a graphics image. By allocating the embedded memory for these purposes, the overall processing speed of the graphics processing system is increased.
Allocation of the embedded memory is typically performed by the graphics application executing on the graphics processing system, and is often allocated according to a priority defined by the graphics application. That is, a portion of the embedded memory is first reserved for a primary purpose requiring a certain amount of memory, such as for z-buffering. Any remaining embedded memory is then allocated to a secondary purpose, such as for pixel buffering. If the memory requirements for the secondary purpose exceed the amount of embedded memory remaining after the allocation for the primary purpose, external memory is used to make up for any memory deficiency for the secondary purpose. Typically, the memory of the graphics processing system is first allocated for the z-buffer, then for the pixel buffer, and then for the texture buffer.
A problem that arises with the graphics application allocating memory is that memory allocation is typically made without regard to the availability of embedded memory in the graphics processing system. As a result, the embedded memory may be allocated in a fashion that reduces overall processing efficiency. For example, where allocation of memory for the z-buffer consumes a significant portion of embedded memory, it is likely that a good portion of memory allocated to the pixel buffer will consist of external memory. However, external memory generally has slower access times than embedded memory, and consequently, operations involving memory access to the pixel buffer will be relatively slower than if a greater portion of the embedded memory were allocated for the pixel buffer.
A conventional approach to resolving the previously described problem is to design graphics processing systems that include more embedded memory that may be allocated to the various uses. However, this approach increases the cost of the graphics processing system, and, where minimizing the size of the system is desired, including additional embedded memory in the graphics processing system may not be an acceptable approach.
Therefore, there is a need for a memory system and a method having the flexibility to allocate memory in a manner other than determined only by the default allocation method of a graphics application.
SUMMARY OF THE INVENTION
The present invention is directed to a memory system and a method for allocating and accessing memory. The memory system includes first and second addressable memory regions coupled to a memory controller. A first portion of the first addressable memory region is allocated to a first requested memory space, and a second portion of the first addressable memory region is allocated to a second requested memory space. Any remaining portions of the first and second requested memory spaces are remapped to the second addressable memory region. The memory controller includes a register to store a respective offset value and values defining the portions of the first and second addressable memory regions allocated to the first and second logical memory spaces. The memory controller is adapted to access the first addressable memory region in response to receiving a memory address for a location within the first portions of the first and second memory spaces and to access the second addressable memory region in response to receiving a memory address for a location within the second portions of the first and second memory spaces.
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Peterson James R.
Radke William
Dorsey & Whitney LLP
Micro)n Technology, Inc.
Tung Kee M.
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