Browse Prior Art Database

Set Bit/Reset Bit Function to Allow Multiple PD Searches in Parallel

IP.com Disclosure Number: IPCOM000103310D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 49K

Publishing Venue

IBM

Related People

Eikill, RG: AUTHOR [+3]

Abstract

The described solves the problem of handling multiple primary directory (PD) searches from different processors without unnecessary serialization logic in a multiprocessor complex.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 74% of the total text.

Set Bit/Reset Bit Function to Allow Multiple PD Searches in Parallel

      The described solves the problem of handling multiple primary
directory (PD) searches from different processors without unnecessary
serialization logic in a multiprocessor complex.

      One of the problems any multiprocessor system must solve is
primary directory coherency.  A set bit function can help simplify
this problem.

      A primary directory search in a system can be hardwired to
simplify horizontal microcode.

      The primary directory contains special bits that track which
pages in memory have been referenced and which have been modified.
This information is used by storage management in its page aging
algorithm.  It is important never to lose a change bit or a reference
bit in main store.

      Invention details:
      -  Provides a set and reset bit function at the memory card.
This function is done as a read/modify/write.
      -  The primary directory search algorithm uses "set bit"
function to set the reference and change bits.
      -  Since the memory cards do the read/modify "set bit"
function, no semaphores are necessary.  It is legal to have multiple
primary directory searches from different processors going on
concurrently.
      -  Provides set bit and reset bit function to horizontal
microcode.  Horizontal microcode can use the function to turn other
bits in the primary directory status byte on and off without
quiescing the...