Browse Prior Art Database

Programmable Cache Decoder

IP.com Disclosure Number: IPCOM000119712D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Aldereguia, A: AUTHOR [+4]

Abstract

This article describes a technique which allows a computer operating system to control the areas of memory it does not want to be cached, especially in a multi-master system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 63% of the total text.

Programmable Cache Decoder

      This article describes a technique which allows a
computer operating system to control the areas of memory it does not
want to be cached, especially in a multi-master system.

      Typically in a cache system, the hardware is designed to decode
an area of memory that is to be cacheable.  In this method the decode
is hardwired and can only be modified by redesigning the hardware.

      The technique of this disclosure eliminates the hardwired
cacheable decode address range.  It allows for the areas of memory
that are cacheable to be programmable, which increases flexibility of
the system.  In this method instead of decoding areas of memory that
are cacheable, areas of memory that are not cacheable are decoded.
There are always some address ranges in memory which are
noncacheable, and some address ranges in memory the operating system
may want to specify as noncacheable.

      The drawing is a functional block diagram of this method which
sets up N number of registers dedicated to disabling cacheability.
These registers are programmable by the operating system.  A set of
comparators can be set up to trap on the addresses that are
noncacheable, with some additional logic performing the invalidation.

      An additional register is the comparator enable register, which
contains an enable bit for each address range register in the system.
When the address range registers are programmed, the bit
corresponding to that re...