Abstract: One embodiment of the present invention sets forth a technique for parallel distribution of primitives to multiple rasterizers. Multiple, independent geometry units perform geometry processing concurrently on different graphics primitives. A primitive distribution scheme delivers primitives from the multiple geometry units concurrently to multiple rasterizers at rates of multiple primitives per clock. The multiple, independent rasterizer units perform rasterization concurrently on one or more graphics primitives, enabling the rendering of multiple primitives per system clock.

Abstract: A method and system are disclosed for antialiased rendering a plurality of pixels in a computer system. The method and system comprise providing a fixed storage area and providing a plurality of sequential format levels for the plurality of pixels within the fixed storage area. The plurality of format levels represent pixels with varying degrees of complexity in subpixel geometry visible within the pixel. A system and method in accordance with the present invention provides at least the following format levels: one-fragment format, used when one surface fully covers a pixel; two-fragment format, used when two surfaces together cover a pixel; and multisample format, used when three or more surfaces cover a pixel. The method and system further comprise storing the plurality of pixels at a lowest appropriate format level within the fixed storage area, so that a minimum amount of data is transferred to and from the fixed storage area.

Abstract: One embodiment of the present invention sets forth a technique for converting alpha values into pixel coverage masks. Geometric coverage is sampled at a number of “real” sample positions within each pixel. Color and depth values are computed for each of these real samples. Fragment alpha values are used to determine an alpha coverage mask for the real samples and additional “virtual” samples, in which the number of bits set in the mask bits is proportional to the alpha value. An alpha-to-coverage mode uses the virtual samples to increase the number of transparency levels for each pixel compared with using only real samples. The alpha-to-coverage mode may be used in conjunction with virtual coverage anti-aliasing to provide higher-quality transparency for rendering anti-aliased images.

Abstract: One embodiment of the present invention sets forth a technique for performing a memory access request to compressed data within a virtually mapped memory system comprising an arbitrary number of partitions. A virtual address is mapped to a linear physical address, specified by a page table entry (PTE). The PTE is configured to store compression attributes, which are used to locate compression status for a corresponding physical memory page within a compression status bit cache. The compression status bit cache operates in conjunction with a compression status bit backing store. If compression status is available from the compression status bit cache, then the memory access request proceeds using the compression status. If the compression status bit cache misses, then the miss triggers a fill operation from the backing store. After the fill completes, memory access proceeds using the newly filled compression status information.

Abstract: A raster unit generates graphic data for specific regions of a display device by processing each graphics primitive in a sequence of graphics primitives. A tile coalescer within the raster unit receives graphic data based on the sequence of graphics primitives processed by the raster unit. The tile coalescer collects graphic data for each region of the display device into a different bin before shading and then outputs each bin separately.

Abstract: A system and method for dynamically adjusting the pixel sampling rate during primitive shading can improve image quality or increase shading performance. Hybrid antialiasing is performed by selecting a number of shaded samples per pixel fragment. A combination of supersample and multisample antialiasing is used where a cluster of sub-pixel samples (multisamples) is processed for each pass through a fragment shader pipeline. The number of shader passes and multisamples in each cluster can be determined dynamically for each primitive based on rendering state.

Abstract: A system and method for dynamically adjusting the pixel sampling rate during primitive shading can improve image quality or increase shading performance. Hybrid antialiasing is performed by selecting a number of shaded samples per pixel fragment. A combination of supersample and multisample antialiasing is used where a cluster of sub-pixel samples (multisamples) is processed for each pass through a fragment shader pipeline. The number of shader passes and multisamples in each cluster can be determined dynamically for each primitive based on rendering state.

Abstract: One embodiment of the present invention sets forth a technique for compressing color data. Color data for a tile including multiple samples is compressed based on an equality comparison and a threshold comparison based on a programmable threshold value. The equality comparison is performed on a first portion of the color data that includes at least exponent and sign fields of floating point format values or high order bits of integer format values. The threshold comparison is performed on a second portion of the color data that includes mantissa fields of floating point format values or low order bits of integer format values. The equality comparison and threshold comparison are used to select either computed averages of the pixel components or the original color data as the output color data for the tile. When the threshold is set to zero, only tiles that can be compressed without loss are compressed.

Abstract: One embodiment of the present invention sets forth a technique for rendering graphics primitives in parallel while maintaining the API primitive ordering. Multiple, independent geometry units perform geometry processing concurrently on different graphics primitives. A primitive distribution scheme delivers primitives concurrently to multiple rasterizers at rates of multiple primitives per clock while maintaining the primitive ordering for each pixel. The multiple, independent rasterizer units perform rasterization concurrently on one or more graphics primitives, enabling the rendering of multiple primitives per system clock.

Abstract: A method for compressing framebuffer data is presented. The method includes determining a reduction ratio for framebuffer data in a tile including multiple samples. The reduction ratio determined is independent of the sampling mode, where the sampling mode is the number of samples within each pixel in the tile. The method further includes comparing a first portion of the framebuffer data for each of the multiple samples to determine an equality comparison result and also comparing a second portion of the framebuffer data for each one of the multiple samples to compute per-channel differences for each one of the multiple samples and testing the per-channel differences against a threshold value to determine a threshold comparison result. Finally, the method comprises compressing the framebuffer data for the tile based on the reduction ratio, the equality comparison result and the threshold comparison result to produce output framebuffer data for the tile.

Abstract: A method and system for selective enablement of tile compression. The method includes receiving a graphics primitive for processing in a set-up unit of a graphics processor and determining a primitive characteristic that indicates a probability of whether a final compression of a tile related to the primitive will be retained. Compression for the tile related to the primitive is allowed when the characteristic indicates the final compression will be retained. Compression for the tile related to the primitive is disallowed in the characteristic indicates the final compression will not be retained.

Abstract: A method and system for overriding state information programmed into a processor using an application programming interface (API) avoids introducing error conditions in the processor. An override monitor unit within the processor stores the programmed state for any setting that is overridden so that the programmed state can be restored when the error condition no longer exists. The override monitor unit overrides the programmed state by forcing the setting to a legal value that does not cause an error condition. The processor is able to continue operating without notifying a device driver that an error condition has occurred since the error condition is avoided.

Abstract: One embodiment of the present invention sets forth a technique for compressing image data with high contrast between pixels within a tile and between samples within pixels without any data loss. Partial coverage layers are generated and written to a tile that includes multiple pixels without reading the existing image data that is stored for the tile. A partial coverage layer encodes image data, such as colors, and sub-pixel coverage information for each covered pixel in a tile. The use of partial coverage layers reduces the bandwidth used to store image data when a tile is not fully covered.

Abstract: Write operations to a unit of compressible memory, known as a compression tile, are examined to see if data blocks to be written completely cover a single compression tile. If the data blocks completely cover a single compression tile, the write operations are coalesced into a single write operation and the single compression tile is overwritten with the data blocks. Coalescing multiple write operations into a single write operation improves performance, because it avoids the read-modify-write operations that would otherwise be needed.

Abstract: A method and system for improving data coherency in a parallel rendering system is disclosed. Specifically, one embodiment of the present invention sets forth a method for managing a plurality of independently processed texture streams in a parallel rendering system that includes the steps of maintaining a time stamp for a group of tiles of work that are associated with each of the plurality of the texture streams and are associated with a specified area in screen space, and utilizing the time stamps to counter divergences in the independent processing of the plurality of texture streams.

Abstract: One embodiment of the present invention sets forth a system and method for supporting high-throughput virtual to physical address translation using compressed TLB cache lines with variable address range coverage. The amount of memory covered by a TLB cache line depends on the page size and page table entry (PTE) compression level. When a TLB miss occurs, a cache line is allocated with an assumed address range that may be larger or smaller than the address range of the PTE data actually returned. Subsequent requests that hit a cache line with a fill pending are queued until the fill completes. When the fill completes, the cache line's address range is set to the address range of the PTE data returned. Queued requests are replayed and any that fall outside the actual address range are reissued, potentially generating additional misses and fills.

Abstract: A system and method for performing zero-bandwidth-clears reduces external memory accesses by a graphics processor when performing clears and subsequent read operations. A set of clear values is stored in the graphics processor. Each region of a color or z buffer may be configured using a zero-bandwidth-clear command to reference a clear value without writing the external memory. The clear value is provided to a requestor without accessing the external memory when a read access is performed.

Abstract: A system and method for performing zero-bandwidth-clears reduces external memory accesses by a graphics processor when performing clears and subsequent read operations. A set of clear values is stored in the graphics processor. Each portion of a color or z buffer may be configured using a zero-bandwidth-clear command to reference a clear value without writing the external memory. The clear value is provided to a requestor without accessing the external memory when a read access is performed.

Abstract: A method and system for overriding state information programmed into a processor using an application programming interface (API) avoids introducing error conditions in the processor. An override monitor unit within the processor stores the programmed state for any setting that is overridden so that the programmed state can be restored when the error condition no longer exists. The override monitor unit overrides the programmed state by forcing the setting to a legal value that does not cause an error condition. The processor is able to continue operating without notifying a device driver that an error condition has occurred since the error condition is avoided.

Abstract: The current invention involves new systems and methods for computing per-sample post-z test coverage when the memory is organized in multiple partitions that may not match the number of shaders. Shaded pixels output by the shaders can be processed by one of several z raster operations units. The shading processing capability can be configured independent of the number of memory partitions and number of z raster operations units. The current invention also involves new systems and method for using different z test modes with multiple render targets with a single or multiple memory partitions. Rendering performance may be improved by using an early z testing mode is used to eliminate non-visible samples prior to shading.