Apple Inc.

Apple Comptuer, Inc.

Bruce E Eckstein

Kevin M Christiansen

Mark Adrian Stubbs

David V James

Michael K Eneboe

A method for reprogramming a video input device to multiplex video data from at least two different video sources is disclosed. A video input device contains control registers for controlling the behavior of the video input device. At least first video data from a first source and a second video data from a second source are received at the video input device. Information about the video data is sent to a controller which generates reprogramming data based on the information. The reprogramming data is transmitted to the video input device, wherein the reprogramming data reprograms the operation of the control registers. Portions of the first and second video data are outputted based upon how the control registers are reprogrammed.

Method of and apparatus for reprogramming a video controller

The present invention is directed to providing a computer system which arbitrates control of a shared bus among plural devices included in the computer system. In accordance with the present invention, at least one of the devices is afforded a higher priority than the remaining devices, yet none of the remaining devices are effectively denied system bus access or control for extended periods of time. The present invention can therefore increase operating efficiency even as the number of devices included in the computer system is increased to achieve enhanced processing power. In addition, the present invention can provide sophisticated multimedia features, including real time signal processing, without sacrificing overall operating efficiency. In accordance with the present invention, the plural devices arbitrate system bus control in a manner which achieves acceptable multimedia results when processing real time data streams such as video data streams, audio data streams, animation data streams, and so forth, yet which does not sacrifice the access of remaining devices in the computer system to the shared bus.

Method and apparatus for arbitration and access to a shared bus

An apparatus for and method of arbitrating bus conflicts is disclosed. The system can use information about the status of a data stream to switch between more or less restrictive prioritization schemes. In one particular embodiment, the arbitration system can also be programmed by causing it to store information on overall system requirements for data which the arbitration system can then use to set a current prioritization scheme.

Apparatus for and method of arbitrating bus conflicts

Method and apparatus for arbitrating access to a shared bus

A DMA controller capable of conditional action under the control of a status register, prespecified parameters, and a condition field of the channel command, and a DMA controller which returns status information to command entry locations that are reserved for this purpose are disclosed. The prespecified parameters may be held in a register having a mask field and a value field, and a test for conditional action may be a masked comparison of the status register and the value field. The condition field determines how the test result is interpreted and allows suppressing or forcing the conditional action during a command.

DMA controller with mechanism for conditional action under control of

The present invention is therefore directed to enhancing the efficiency with which input/output controllers execute operations in response to requests from another device, such as a main controller. In accordance with exemplary embodiments, a compact set of status information signals is communicated from an input/output controller to a main controller such that the main controller can provide error control (that is, monitor input/output controller operation) without the use of interrupts. As a result, the main controller can sequentially and continuously supply multiple commands of a transaction to the input/output controller without the use of a multiple hardware interrupts. System hardware can therefore be used more efficiently and input/output controller operation can be accelerated, thereby increasing system performance.

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Cupertino, CA, United States of America

Bruce E Eckstein