Abstract: One embodiment of the present invention sets forth a technique for improving graphics rendering efficiency by processing pixels in a compressed format whenever possible within a multi-sampling graphics pipeline. Each geometric primitive is rasterized into fragments, corresponding to screen space pixels covered at least partially by the geometric primitive. Fragment coverage represents the pixel area covered by the geometric primitive and determines the weighted contribution of a fragment color to the corresponding screen space pixel. Samples associated with a given fragment are called sibling samples and have the same color value. The property of sibling samples having the same color value is exploited to compress and process multiple samples, thereby reducing the size of the associated logic and the amount of data written to and read from the frame buffer.

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.

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.

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 graphics pipeline architecture for optimizing graphics rendering efficiency by advancing the Z-test operation prior to shading operations whenever possible, as determined by an upstream pipeline configuration unit. Each processing engine within the graphics pipeline maintains independent state for both early Z-mode and late Z-mode operations and also may maintain state common to both modes. The processing engines receive work transactions that include a Z-mode flag indicating whether the work transaction should be processed in late Z-mode or early Z-mode. The Z-mode flag is also used to dynamically route any resulting outbound data, so that the appropriate data flow for either early Z or late Z processing is dynamically constructed for each work transaction.

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: 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: A parallel array architecture for a graphics processor includes a multithreaded core array including a plurality of processing clusters, each processing cluster including at least one processing core operable to execute a pixel shader program that generates pixel data from coverage data; a rasterizer configured to generate coverage data for each of a plurality of pixels; and pixel distribution logic configured to deliver the coverage data from the rasterizer to one of the processing clusters in the multithreaded core array. A crossbar coupled to each of the processing clusters is configured to deliver pixel data from the processing clusters to a frame buffer having a plurality of partitions.

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, which includes the steps of receiving a common input stream, tracking a periodic event associated with the common input stream, generating a plurality of fragment streams from the common input stream, inserting a marker based on an occurrence of the periodic event in a first fragment stream in the multiple fragment streams, and utilizing the marker to influence the processing of the first fragment stream so that a plurality of raster operation (ROP) request streams maintains substantially the same coherence as the common input stream. Each fragment stream is independently processed and corresponds to one of the ROP request streams.

Abstract: A method of performing a blit operation in a parallel processing system includes dividing a blit operation into batches of pixels, performing reads of pixels associated with a first batch in any order, confirming that all reads of pixels associated with the first batch are completed, and performing writes of pixels associated with the first batch in any order. The pixels of the first batch and pixels of additional batches are applied to parallel processors, where the parallel processors include a corral defined by entry points and exit points distributed across the parallel processors.

Abstract: A tiled graphics memory permits graphics data to be stored in different tile formats. One application is selecting a tile format optimized for the data generated for particular graphical surfaces in different rendering modes. Consequently, the tile format can be selected to optimize memory access efficiency and/or packing efficiency. In one embodiment a first tile format stores pixel data in a format storing two different types of pixel data whereas a second tile format stores one type of pixel data. In one implementation, a z-only tile format is provided to store only z data but no stencil data. At least one other tile format is provided to store both z data and stencil data. In one implementation, z data and stencil data are stored in different portions of a tile to facilitate separate memory accesses of z and stencil data.

Abstract: A system and method are described for compressing image data using a combination of compression methods. Compression method combinations are provided to compress image data of a particular frame buffer format and antialiasing mode. Each method in the compression method combination is tried in turn to compress the image data in a tile. The best method that succeeded in compressing the image data is encoded in the compression bit state associated with the tile. Together, the compression bits, the compression method combination, and the frame buffer format provide sufficient information to decompress a tile.

Abstract: Methods and systems for reusing memory addresses in a graphics system are disclosed, so that instances of address translation hardware can be reduced. One embodiment of the present invention sets forth a method, which includes mapping a footprint on a display screen to a group of contiguous physical memory locations in a memory system, determining an anchor physical memory address from a first transaction associated with the footprint, wherein the anchor physical memory address corresponds to an anchor in the group of contiguous physical memory locations, determining a second transaction that is also associated with the footprint, determining a set of least significant bits (LSBs) associated with the second transaction, and combining the anchor physical memory address with the set of LSBs associated with the second transaction to generate a second physical memory address for the second transaction, thereby avoiding a second full address translation.

Abstract: Methods and systems for reusing memory addresses in a graphics system are disclosed, so that instances of address translation hardware can be reduced. One embodiment of the present invention sets forth a method, which includes mapping a footprint in screen space to a group of contiguous physical memory locations in a memory system, determining a first physical memory address for a first transaction associated with the footprint, wherein the first physical memory address is within the group of contiguous physical memory locations, determining a second transaction that is also associated with the footprint, determining a set of least significant bits associated with the second transaction, and combining a portion of the first physical memory address with the set of least significant bits associated with the second transaction to generate a second physical memory address for the second transaction, thereby avoiding a second full address translation.

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 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: 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 synchronization mechanism is used to synchronize events across multiple execution pipelines that process transaction streams. A common set of state configuration is included in each transaction stream to control processing of data that is distributed between the different transaction streams. Portions of the state configuration correspond to portions of the data. Execution of the transaction streams is synchronized to ensure that each portion of the data is processed using the state configuration that corresponds to that portion of the data. The synchronization mechanism may be used for multiple synchronizations and when the synchronization signals are pipelined to meet chip-level timing requirements.

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.