3dlabs Inc., Ltd.

Simon James Moore

David Robert Baldwin

Neil F Trevett

Malcolm E Wilson

John W Neave

Andrew Peter Maund

A system and method for increasing rendering efficiency in pipelined graphics systems. In the disclosed embodiments, reads of pixel information during the rendering of a primitive are suspend if the pixel information has not been updated by a previous primitive. In some embodiments, reads of pixel information are also suspended periodically when a table tracking the information becomes full. In some embodiments a Read Monitor Unitcontrolled by the graphics system's Memory Controlleris used to track pixels which have been affected by rendered primitives. In some embodiments, a history list is used to avoid suspension of reads for antialiased lines. In a particular embodiment, the table used to track affected pixels is two-bits, the first bit tracking whether the pixel has been touched by a primitive since the last SuspendReads command was invoked and the second bit tracking whether the pixel has been touched by the current primitive. Both bits are reset when a power on or SuspendReads command occurs. The second bit is also reset at the start of rendering for each primitive. In a separate embodiment, a unique number is assigned to each primitive to be rendered. The number is recorded for each active pixel touched by the primitive. If an earlier primitive has touched this pixel, suspension of reads can be invoked and the table reset (i.e., every entry is marked invalid).

3D graphics rendering with selective read suspend

In a demand-paged virtual memory system, the pages are arranged in the virtual memory space in groups. In order to translate an address from the virtual address space to a physical memory address space, the virtual group address component is input to a contents addressable memory (767), which outputs a group code (767), and the group code and virtual page address component (768X,Y) are input to a RAM page table (750) which outputs the page address. When the physical memory capacity is substantially smaller than the virtual address space, the CAM provides a large saving in page table size. In the case where the data-elements provide a plural-dimensional representation, for example as in pixel data, the pages include data elements which are contiguous in each of the plural dimensions in order to reduce the amount of page-swapping between the physical memory and a paging memory. The data-elements in the physical memory are accessible in parallel as contiguous patches. In order to allow parallel access of patches which are not aligned with respect to a page and therefore may fall partly on the edge of one page and partly on the edge of a page which is contiguous with the first page in the virtual memory but not in the physical memory, the addressing system determines whether a patch to be accessed has data-elements in different pages, and may then modify the addresses to the physical memory.

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Horsham, United Kingdom

Simon James Moore