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From: soohong@gondor.cs.psu.edu (Soohong Kim)
Newsgroups: comp.arch
Subject: Help: Hashing on TLB input?
Keywords: TLB, hashing
Message-ID: <3907@psuvax1.cs.psu.edu>
Date: 8 Sep 88 23:10:37 GMT
Sender: news@psuvax1.cs.psu.edu
Reply-To: soohong@gondor.cs.psu.edu (Soohong Kim)
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Organization: Penn State University
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Could some one please enlighten me by explaining these?

    In Hwang & Briggs (Computer architecture and parallel processing) it is
said that the virtual page number is first randomized by hashing before
feeding it to the TLB. It is also said that the reason is for efficient use
of the low-order TLB entries. And Vax/750 seems to avoid hashing by using
a number of high-order bits and 5 low-order bits to select the set in the
set-associative TLB.

    My questions are:
(1) Why is it inefficient to use the Virtual page number directly?
(2) How could hashing or bit-combination help in improving the efficiency?

Thank you.
---Soohong