Abstract:
In a computer system, a FIFO (first-in-first-out) queue is utilized to provide control information to the appropriate time slot in a time multiplexed serial link between an interface chip and a CODEC. The FIFO queue allows rewriting or replacement of any control registers present in the queue without requiring that a new entry be placed in the queue. A particular control register which is placed in the queue then maintains its place as the queue is emptied, even though the control register may be written one or more times while the control register entry is in the queue waiting for transmission to the CODEC. The loss of the prior command information is not a problem as the data rate of the serial link is still sufficiently high so that any minor transitory change which may have been desired would be of minimal effect in any regard and would have been inaudible to the human.
Abstract:
A computer system includes a microprocessor coupled to a main memory through a bridge logic unit. The bridge logic unit receives memory read requests from the microprocessor and provides the requests to the main memory. The bridge logic unit includes a memory fetch control unit configured to fetch a single line of data from the main memory in response to an initial read request from the microprocessor. If a read request to a sequential line of data is received from the microprocessor, the memory fetch control unit fetches not only the requested line of data but also the next sequential line of data. Thus, following the initial read request in which a single line of data is fetched, when the microprocessor issues a request for data from a sequential line, that line is fetched and the subsequent line is speculatively prefetched. If the microprocessor continues with a request to yet an additional sequential line, the memory fetch unit continues its speculative generation of a request for the next sequential line. If the microprocessor issues a memory read request to a non-sequential line of data, the memory fetch control unit fetches only that line of data.
Abstract:
A computer system having an expansion base for docking a portable portion of the computer system includes a bridge circuit for adaptively decoding addresses on a bus based on the docking status. Both the expansion base and the portable portion include the bridge circuit for passing cycles from a peripheral component interconnect (PCI) bus to an industry standard architecture (ISA) bus. The bridge includes internal devices and configuration registers for controlling the decoding. Bus cycles intended for internal devices and external devices connected to each respective ISA bus of the bridge circuits are positively decoded. Cycles not positively decoded and claimed are subtractively decoded by one of the bridge circuits depending on the docking status.
Abstract:
An arbitration scheme for a computer system having multiple arbiters for arbitrating access to a plurality of buses. In the preferred embodiment, a computer system is divided into a detachable laptop portion and an expansion base unit coupled through a shared PCI bus. Each of the two portions of the computer system includes separate PCI arbitration circuitry for arbitrating requests for the PCI bus from potential PCI and ISA bus masters. Included within the laptop portion of the computer system is a top level arbiter that determines whether the PCI arbiter in the laptop or expansion base unit has access to the PCI bus. Either PCI arbiter normally must receive a grant from the top level arbiter before it runs a cycle. While the laptop computer is docked, the top level arbiter selects between the PCI arbiters on an essentially time multiplexed basis. While the expansion base and laptop computer are undocked, the top level arbiter grants bus access to the laptop PCI arbiter.
Abstract:
A computer system having separate, yet compatible DMA controllers on a bus. Each DMA controller for controlling at least one DMA channel, each DMA controller having an independent set of registers for performing DMA operations and a configuration register for indicating channel status and designation. A DMA master for compatibly communicating with a processor and for initializing and communicating with the multiple DMA controllers.
Abstract:
An arbitration scheme for a computer system having multiple arbiters for arbitrating access to a plurality of buses. In the preferred embodiment, a computer system is divided into a detachable laptop portion and an expansion base unit coupled through a shared PCI bus. Each of the two portions of the computer system includes separate PCI arbitration circuitry for arbitrating requests for the PCI bus from potential PCI and ISA bus masters. Included within the laptop portion of the computer system is a top level arbiter that determines whether the PCI arbiter in the laptop or expansion base unit has access to the PCI bus. Either PCI arbiter normally must receive a grant from the top level arbiter before it runs a cycle. While the laptop computer is docked, the top level arbiter selects between the PCI arbiters on an essentially time multiplexed basis. While the expansion base and laptop computer are undocked, the top level arbiter grants bus access to the laptop PCI arbiter.
Abstract:
A computer system includes a microprocessor coupled to a main memory through a bridge logic unit. The bridge logic unit receives memory read requests from the microprocessor and provides the requests to the main memory. The bridge logic unit includes a memory fetch control unit configured to fetch a single line of data from the main memory in response to an initial read request from the microprocessor. If a read request to a sequential line of data is received from the microprocessor, the memory fetch control unit fetches not only the requested line of data but also the next sequential line of data. Thus, following the initial read request in which a single line of data is fetched, when the microprocessor issues a request for data from a sequential line, that line is fetched and the subsequent line is speculatively prefetched. If the microprocessor continues with a request to yet an additional sequential line, the memory fetch unit continues its speculative generation of a request for the next sequential line. If the microprocessor issues a memory read request to a non-sequential line of data, the memory fetch control unit fetches only that line of data.