US 4,417,334 A · Data processing system having dual-channel system bus

Abstract

A data processing system employing broadcast packet switching and having a plurality of subsystems and a system bus for linking the subsystems. The subsystems are grouped within stations that are each enclosed by a computer cabinet. The system bus includes a star coupler, first and second external transmission lines connecting each station to the star coupler, and first and second internal transmission lines within each station that are coupled to the first and second external transmission lines. The subsystems within each station are each coupled to the first and second internal transmission lines by a system bus interface. The system bus interface monitors the system bus for an idle condition, and passes a message from its subsystem to the system bus only when it detects an idle condition on the system bus. Each message on the system bus includes a postamble that is garbled by any system bus interface that detects an error in any message on the system bus. Each subsystem has a local memory that includes a mailbox for storing header information of messages that are to be copied by that subsystem. DMA circuitry in each system bus interface manages the operation of the mailbox in its subsystem. In alternate embodiments, the star coupler may be a magnetic star coupler or an electrical star coupler, and the system bus may be comprised of two channels, each channel including a star coupler and pairs of transmission lines connecting each station to the star coupler.

Claims17

Dependent claims

A data processing system, comprising:

a plurality of stations, wherein each station includes at least one data processor and a memory storing data for said processor;
a first star coupler;
a second star coupler;
and
first and second pairs of transmission lines associated with each station, said first pair of transmission lines connected between its associated station and said first star coupler, said second pair of transmission lines connected between its associated station and said second star coupler, with each of said first and second pairs of transmission lines including a first transmission line for carrying signals from its associated station and a second transmission line for carrying signals to its associated station, so that signals transmitted by any of said stations may be passed through either said first star coupler or said second star coupler and be received by all of said stations.

2 more elements

In a data processing system of the type employing broadcast packet switching and having a plurality of subsystems, wherein each subsystem includes a processor for processing data and a memory for storing data for said processor, a communications channel for carrying messages between said subsystems so that a message transmitted by any one of said subsystems is passed by said channel to all of said subsystems, means associated with each subsystem for detecting whether the channel is idle and not carrying a message so that its associated subsystem transmits a message only if the channel is detected as idle, and means associated with each subsystem for receiving the message carried on the channel and for comparing the received message to the message being transmitted by its associated subsystem, to detect whether the transmitted message is being garbled by the simultaneous transmission of a message by another subsystem, the improvement comprising:

a second communications channel for carrying messages between said subsystems so that a message transmitted by any one of said subsystems may be passed by said second channel to all of said subsystems, said second channel carrying messages independently of said first-mentioned channel so that a message transmitted by any one of said subsystems may be transmitted either on said first-mentioned channel or said second channel, without the messages on each of said first-mentioned channel and said second channel interfering with each other.

A system bus interface for a data processing system employing broadcast packet switching and having a plurality of subsystems and a system bus including two channels for each carrying messages between said subsystems, wherein said data processing system employs broadcast packet switching with a message transmitted by one of said subsystems to be carried on one of said two channels only if that channel is idle and not already carrying a message, and wherein one said system bus interface is associated with each of said subsystems for coupling its associated subsystem to said system bus, said system bus interface comprising:

means for detecting whether either one of said two channels of said system bus is idle and not carrying a message;
channel selection means responsive to said means for detecting for passing a message to be carried on said system bus to a selected one of said two channels if said selected one of said two channels is idle;
address check means connected for receiving messages carried on each of said two channels to determine if the associated subsystem is the destination of any one of the messages;
and
receive control means responsive to said address check means for passing a message from said system bus to the associated subsystem if the associated subsystem is the destination of the message, including means for passing only one message if a message is carried on each of said two channels at the same time and the destination of each message is the associated subsystem.

2 more elements

Dependencies are inferred from the claim text.

Data processing system having dual-channel system bus

Life of this patent

Data processing system having dual-channel system bus

Life of this patent

Abstract

Claims17