Browse Prior Art Database

Cacheless Page Override

IP.com Disclosure Number: IPCOM000109132D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Funk, MR: AUTHOR [+3]

Abstract

A control over the entries of a lookaside buffer used in virtual address translation forces subsequent storage accesses to pages addressed via lookaside buffer entries to bypass the cache and access main storage directly.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 92% of the total text.

Cacheless Page Override

      A control over the entries of a lookaside buffer used in
virtual address translation forces subsequent storage accesses to
pages addressed via lookaside buffer entries to bypass the cache and
access main storage directly.

      A common practice in the support of store-in caches is to
define a virtual address translation mode where the data in main
storage is not brought into the cache when accessed.  That is, the
access goes directly to main store and does not affect the contents
of the cache directory.  This is true on both fetches and stores of
the associated data.  This mode indicator is found in the translation
tables in main store and is reflected in the Translation Lookaside
Buffer (TLB).  Holding the indicator in the TLB assures that
subsequent accesses to the associated page also bypass the cache.

      The intent of this invention is to override the normal cache
control mechanism associated with a page, using the previously
existing cache control indicators held in the TLB.

      The invention is a translation control or store command which
indicates that an address which is not already in the TLB should be
marked in the TLB as being "cacheless".  For the length of time that
this page remains in this TLB entry, all subsequent stores to this
page bypass the cache and do not result in cache line fills.  Once
the address is removed from the TLB, due to aging or explicitly,
subsequent accesses to that page use the...