Digital Equipment Corporation

Compaq Computer Corporation, Inc.

Elbert Bloom

David W Hartwell

Victoria M Triolo

David Martin Fenwick

Denis J Foley

Ricky C Hetherington

Stephen R Van Doren

Dale R Keck

In accordance with the present invention, an apparatus includes a system bus having memory bank available signals. Coupled to the system bus are at least two memory modules, each having at least one memory bank. Each memory module includes a mechanism for associating each memory bank with one of the memory bank available signals. Further, each memory module includes logic for determining an availability status of each memory bank and for providing the associated memory bank busy signal with values reflecting the availability status of the memory bank. Additionally, at least two commander modules are coupled to the system bus and include logic, responsive to the memory bank available signals for preventing the commander module from gaining control of the system bus when the commander is attempting to access a memory bank determined to be unavailable. With such an arrangement, only commander modules seeking to access memory banks which are available will be allowed to gain control of the system bus. This avoids stalling the system bus and improves system performance by allowing all initiated transactions to complete as quickly as possible.

Apparatus for determining memory bank availability in a computer system

A data bus sequencer for use by nodes coupled to a system bus for associating data transactions and address transactions on the bus. The data bus sequencer includes means for tracking address and command transactions occurring on an address bus, the means for tracking producing a sequence number tag corresponding to each address and command transaction occurring on the address bus. Means for associating data transactions with address and command transactions stores the sequence number tags corresponding to address and command transactions for which data transactions are to be initiated by the node. Further included are means for tracking data transactions occurring on a data bus, means for comparing tracked data transactions to associated data transactions, and means for initiating data transactions on the data bus in response to the comparison. The data bus sequencer further includes means for driving the sequence tag for an address and command transaction to which a data transaction is associated on the data bus. Consistency check means includes means for tracking data transactions occurring on a data bus, and means for comparing tracked data transactions to sequence number tags driven on the data bus. The consistency check means indicates an error condition in response to the comparison if the sequence number tag most recently driven on the data bus is not equal to the counted number of data transactions which have occurred on the data bus.

Distributed data bus sequencing for a system bus with separate address

A data bus sequencer for use by nodes coupled to a system bus for associating data transactions and address transactions on the bus. A mechanism for tracking address and command transactions occurring on the bus produces, for each address and command transaction occurring on the address bus, a corresponding sequence number tag. Those sequence number tags corresponding to address and command transactions for which data transactions are to be initiated by the node are stored by the data bus sequencer. The data bus sequencer further includes circuitry for counting the number of data transactions occurring on the data bus, comparing the counted number of data transactions to the stored sequence number tags and initiating data transactions on the data bus in response to the comparison.

A bus adapter connecting a high-speed pended bus to a slower speed non-pended bus includes a first module functioning as a node of the pended bus and a second module functioning as a node of the non-pended bus. An interconnect bus extends between the two modules. Control signals on the interconnect bus generated by the first module comprise status signals having an indefinite assertion duration, and are deasserted only in response to control signals on the interconnect bus generated by the second module, which have a finite duration. Control signals on the interconnect bus generated by the first module are synchronized by a dual-rank synchronizer controlled by two phases of a multiphase clock signal derived from the clock signal of the non-pended bus. Control signals on the interconnect bus generated by the second module are synchronized by a dual-rank synchronizer controlled by two phases of a multiphase clock signal derived from the pended bus clock signal.

Method and apparatus for interconnecting busses in a multibus computer

A control adapter module in a bus adapter connecting a high-speed pended bus to a slower speed non-pended bus functions as a node of the non-pended bus. An interconnect bus extends between the control module and a response adapter module functioning as a node on the pended bus. Control signals on the interconnect bus generated by the response module comprise status signals having an indefinite assertion duration, and are deasserted only in response to control signals on the interconnect bus generated by the control module, which have a finite duration. Control signals on the interconnect bus generated by the response module are synchronized by a dual-rank synchronizer controlled by two phases of a multiphase clock signal derived from the clock signal of the non-pended bus. Control signals on the interconnect bus generated by the control module are synchronized by a dual-rank synchronizer controlled by two phases of a multiphase clock signal derived from the pended bus clock signal.

Bus adapter module for interconnecting busses in a multibus computer

A bus adapter interconnecting a system bus and an I/O bus over an interconnect bus generates a first READ signal by decoding the command lines of the I/O bus and supplying the READ command signal across the interconnect bus. The command lines are also provided across the interconnect bus and are decoded on the system bus side of the interconnect bus to form a second READ signal. The first and second READ signals and a parity error signal are processed on the system bus side of the interconnect bus to generate a NON-RECOVERABLE ERROR signal to initiate a system shut-down when a parity error occurs during a disconnected WRITE transaction and to generate a RECOVERABLE ERROR signal to initiate a repeat of the transaction when a parity error occurs during a READ transaction.

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Marlboro, MA, United States of America

Elbert Bloom