Electrical computers and digital data processing systems: input/ – Access arbitrating – Access prioritizing
Reexamination Certificate
1998-09-30
2001-12-11
Luu, Le Hien (Department: 2152)
Electrical computers and digital data processing systems: input/
Access arbitrating
Access prioritizing
C710S240000
Reexamination Certificate
active
06330632
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to communications networks. More particularly, the invention relates to a method and apparatus for arbitrating access from multiple requesters to multiple shared resources over a shared communications link.
2. Description of the Prior Art
Arbitration for access to a shared communication link is usually performed with a round robin or priority encoder algorithm. In a typical round robin or priority encoder based arbitration scheme, the choice of which requester is granted access next is made without knowledge of which resource is being accessed. This results in consecutive requests to the same resource. As a result the communication link is idle while the resource completes its post transaction recovery and while it performs its pretransfer setup. This may result in under utilization (loss of efficiency) of the link due to latency in access to the shared resource.
It would be advantageous to provide a method and apparatus for arbitrating access from multiple requestors to multiple shared resources over a shared communications link while minimizing latency and maximizing link utilization.
SUMMARY OF THE INVENTION
The invention provides a method and apparatus for arbitrating for access to a group of shared resources that are communicating with multiple requesters over a shared communications link while minimizing latency and maximizing link utilization. The invention is applicable to any situation where more than one device communicates with more than one resource over a single communication link, and where the cycle time of the resource is greater than the time the link is needed for the transfer by the resource. The invention maintains information about the state of the shared resources. This allows the provision of an arbitration algorithm that uses the shared communications link more efficiently.
A shared resource typically requires some set-up time before transferring its data and also requires some recovery time after its data are transferred before another request may be processed. The invention provides careful selection of the sequence in which requests are serviced which allows one resource to set-up while another resource is still transferring data, and which allows the first resource to complete its recovery while the second resource is transferring data.
REFERENCES:
patent: 5392285 (1995-02-01), Kurts
patent: 5553071 (1996-09-01), Aranguren et al.
patent: 5790786 (1998-08-01), Wakeman et al.
patent: 5832278 (1998-11-01), Pham
patent: 5881313 (1999-03-01), Ramakrishnan et al.
patent: 5884027 (1999-03-01), Garbus et al.
patent: 5941967 (1999-08-01), Zulian
patent: 5941979 (1999-08-01), Lentz et al.
patent: 6154816 (2000-11-01), Steely et al.
Hewlett--Packard Company
Luu Le Hien
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