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Browse Prior Art Database

Arbitration for Multiprocessor Bus Switch

IP.com Disclosure Number: IPCOM000104667D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Chen, WL: AUTHOR

Abstract

An algorithm for arbitrating incoming packets from multiple input ports to an output port in a SCIL switch is disclosed. The algorithm uses a wait priority and the packet send priority to guarantee forward progress, and combines the round-robin to assure fairness.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 59% of the total text.

Arbitration for Multiprocessor Bus Switch

      An algorithm for arbitrating incoming packets from multiple
input ports to an output port in a SCIL switch is disclosed.  The
algorithm uses a wait priority and the packet send priority to
guarantee forward progress, and combines the round-robin to assure
fairness.

ARBITRATION CRITERION

o   Wait count
         The wait count is used to raise the priority of the
    requestor
o   Send-priority (.spr)
         The send-priority is copied from the input packet header
o   Wait-priority (wpr)
         The wait-priority is the highest priority
o   Round robin
         If there are multiple requests with highest priority,
    round-robin
         is used to break the tie.

THE ARBITRATION ALGORITHM

o   The request flags identify the output port m.

o   The output_sel identifies the input port k.

o   The wait count is an N bits counter that is incremented each
    cycle the requestor sees a 'busy' status.  The number of bits in
    the counter would be roughly enough to cover the duration of
    transmitting the largest packet.  Overflow of this counter is
    carried into the send-priority such that the send-priority is
    raised.  This counter starts at zero when the requestor first
    issues a request to own an output port.

o   The send-priority is a 2-bit counter ahead of the wait counter.
    When the wait counter overflows, this counter is...