Browse Prior Art Database

Recoding of Ownership within a Memory Directory

IP.com Disclosure Number: IPCOM000111225D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Baldus, DF: AUTHOR [+3]

Abstract

A method of recoding memory directory occupancy bits to identify a unique device or group of devices when a memory block is owned or held exclusive is described.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Recoding of Ownership within a Memory Directory

      A method of recoding memory directory occupancy bits to
identify a unique device or group of devices when a memory block is
owned or held exclusive is described.

      A memory directory entry is shown below.  When a memory block
is held in an exclusive state by a remote device a valid memory
directory entry will exist.  This entry will be in the exclusive
state.

A memory directory entry contains multiple fields:

-----------------------------------------------------------------
   | State | Device | Occupancy Bits | Real Address | Address Hash |
   -----------------------------------------------------------------
             1 bit       x bits

      This invention adds one bit to each coherency directory entry
called the device bit in the figure above.

      First, assuming the device bit is off, the occupancy bits in
this case are assigned one bit per coherency group.  This group may
represent one or more devices within the system.

      When the entry is in the exclusive state and device bit is on,
the occupancy bits identify a unique device that has been given
exclusive rights to the particular memory block.

      When a device requests exclusive rights to a memory block from
the coherency directory it is determined(by methods that vary by
implementation) if unique device identification is required.  If
identification is required the device bit is set and the dev...