James F Lockwood

US Patent:

53394437, Aug 16, 1994

Filed:

Dec 17, 1992

Appl. No.:

7/991497

Inventors:

James M. Lockwood - San Jose CA

Assignee:

Sun Microsystems, Inc. - Mountain View CA

International Classification:

G06F 1314

US Classification:

395725

Abstract:

In a multiprocessor computer system, an access request and an access grant register is provided for storing an access request and an access grant semaphore for each shared resource. The access request and grant semaphores having a number of access request and grant bits assigned to the processors. Additionally, circuits are provided for each access request register for setting/clearing individual access request bits, and simultaneous reading of all access request bits of the stored access request semaphore. Furthermore, coordinated request and grant masks that reflect the relative access priorities of the processors are provided for the processors to use in conjunction with the current settings of the access request and grant semaphores to determine whether a shared resource is granted to a lower priority processor and whether a shared resource is being requested by a higher priority processor. As a result, multiprocessor accesses to shared resources are arbitrated in a manner having a number of advantages over the prior art.