Browse Prior Art Database

Early Access Mode

IP.com Disclosure Number: IPCOM000100404D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Emma, PG: AUTHOR [+5]

Abstract

When conflicting accesses for the cache involve the use of complementary resources, these accesses can be resolved concurrently by allowing each to use the resources it requires and to sort the result out later. The primary prerequisite of a system which can perform EAM is that it will allow independent activity with the DIRECTORY and the ARRAYS. This assumes that busing of the addresses to the these units is done separately. EARLY ACCESS MODE (EAM) is an example of such a mechanism. EAM causes the arrays of the cache to be referenced before the address used for this reference is sent to the cache directory and arrays.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Early Access Mode

       When conflicting accesses for the cache involve the use
of complementary resources, these accesses can be resolved
concurrently by allowing each to use the resources it requires and to
sort the result out later.  The primary prerequisite of a system
which can perform EAM is that it will allow independent activity with
the DIRECTORY and the ARRAYS. This assumes that busing of the
addresses to the these units is done separately.  EARLY  ACCESS MODE
(EAM) is an example of  such a mechanism.  EAM causes the arrays of
the cache to be referenced before the address used for this reference
is sent to the cache directory and arrays.

      For example, if the BRANCH TARGET FETCH and the STORE PUTAWAY-
LOOKUP vie for the cache bus on the same cycle, the STORE PUTAWAY-
LOOKUP is done by the the CACHE DIRECTORY/DLAT while the BRANCH
TARGET FETCH accesses the ARRAYS.  The result of this array access is
retained until the next cycle when the BRANCH TARGET FETCH uses the
DIRECTORY/ DLAT.  One ARRAY of the cache can be used to perform the
STORE PUTAWAY-UPDATE and the others can respond to a SEQUENTIAL
I-FETCH assuming that the DWI (Double Word Index) indicates no line
crossing.  The resolution of the correct array by the DIRECTORY/DLAT
allows the two sequential I-Fetches to be selected and they are sent
over to the I-Buffer in the proper order.  Such a system also allows
for a guessing opportunity based on MRU after the first access.  If
the gues...