Graphics display system with unified memory architecture
AssigneeBroadcom Corporation
InventorsAlexander G. MacInnis, Chengfuh Jeffrey Tang, Xiaodong Xie, James T. Patterson, Greg A. Kranawetter
Life of this patent
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Abstract
A graphics display system integrated circuit is used in a set-top box for controlling a television display. The graphics display system processes analog video input, digital video input, and graphics input. The system incorporates a unified memory architecture that is shared by the graphics system, a CPU, and other peripherals. The unified memory architecture uses real time scheduling to service tasks. Critical instant analysis is used to find a schedule for memory usage that does not affect memory requirements of real time tasks while at the same time servicing non-real-time tasks as needed.
Claims22
A unified memory system comprising:
- a memory that is shared by a plurality of devices;
- a memory request arbiter coupled to the memory, wherein the memory request arbiter performs real time scheduling of memory requests from different devices having different priorities;
- and
- one or more block out timers, each block out timer being associated with one or more devices and coupled between the one or more associated devices and the memory request arbiter, wherein each block out timer is used to enforce a minimum interval between subsequent accesses by the one or more associated devices,
- wherein the unified memory system provides for real time scheduling of tasks, some of which do not inherently have pre-determined periodic behavior, and for access to memory by devices that are sensitive to latency and do not have determinable periodic behavior.
A method of designing real time scheduling comprising the steps of:
- running a critical instant analysis;
- ordering periods of different tasks from the shortest to the longest;
- assigning priorities based on the order in accordance to the duration of the periods;
- selecting tasks that are non-periodic but requires expedited servicing, assigning high priorities to them, and imposing a minimum interval between successive accesses by these tasks;
- and
- assigning low priority to non-periodic tasks, that do not require expedited servicing, to be serviced in a round robin manner.
Dependencies are inferred from the claim text.