Browse Prior Art Database

Predicting Address Translation with Partial Address Compares

IP.com Disclosure Number: IPCOM000105358D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Liu, L: AUTHOR

Abstract

This invention provides the capability of comparing partial address bits when a history table is utilized to predict virtual address translation information. The advantage is higher accuracy for prediction.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 60% of the total text.

Predicting Address Translation with Partial Address Compares

      This invention provides the capability of comparing partial
address bits when a history table is utilized to predict virtual
address translation information.  The advantage is higher accuracy
for prediction.

      There have been proposals for predicting real address bits for
a virtual address.  A typical example is to employ a 1-dimensional
table (H).  H is indexed by certain (page) address bits to an entry,
from which the predicted information is retrieved without address
compares involved.  Although this gives a fast prediction mechanism,
it was observed from simulations that the accuracy of prediction
could be improved if certain address bits can be used to further
refine the prediction entry selection, particularly in a
set-associative history.

      Consider a history table H, which is set-associative.  Each
entry of H has an ID-tag and a history tag (HIST).  The ID-tag
records certain partial (virtual) address bits and the HIST-tag
records the real address bits to be predicted.  For each virtual
address V that needs to be predicted for real address bits, certain
address bits of V are used to index to a congruence class of H.  From
which certain partial address bits of A are compared with the ID-tags
at all entries of the congruence class.  There are the following
possibilities:

   1.  Partial address compares find a match at one of the entries  -
       In which case t...