Browse Prior Art Database

Caching of the Dat Locking Mechanism on the RISC System/6000

IP.com Disclosure Number: IPCOM000112186D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Bailey, R: AUTHOR [+3]

Abstract

A method for caching of the Data Locking mechanism on the RISC System/6000* is disclosed. This invention allows for nearly doubling the size of the data TLB's over those contained in previous designs.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 70% of the total text.

Caching of the Dat Locking Mechanism on the RISC System/6000

      A method for caching of the Data Locking mechanism on the RISC
System/6000* is disclosed.  This invention allows for nearly doubling
the size of the data TLB's over those contained in previous designs.

      The RISC System/6000 supports Data Locking a protection
mechanism which provides protection to a 128 byte granularity.  Data
Locking may be selectively activated for any 4Kb page in memory.
When active for a page an additional 2 words of Data Locking
information are provided.  In previous designs each TLB entry
contained area for an additional 2 words of Data Locking information.

This nearly doubled the size of the TLB's restricting the the amount
of TLB's contained in a design.

      The method for caching of the Data Locking mechanism is based
on the operating system requirements that only a small number of
pages with Data Locking information will be active at anyone time.
Therefore one can see that having the capability for each TLB to
contain Data Locking information is not necessary.  With this though
in mind a secondary cache to the TLB's was constructed to contain the
Data Locking information.

      The implementation of this secondary cache was as a 16 entry
direct mapped cache.  The Figure shows the TLB and secondary Data
Locking cache used in the processor design.  The amount of area now
used by the Data locking mechanism has been greatly reduced and the
performance has...