Article View: comp.arch
Article #13460Re: Branch prediction in the 532
From: amos
Date: Wed, 22 Apr 1987 15:32
Date: Wed, 22 Apr 1987 15:32
16 lines
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1447 bytes
Looks like the person who wrote the brochure about the 32532 didn't
look at the spec; anyway it's certain that:
1. The whole point of branch prediction is not waiting for the condition
codes; therefore the prediction cannot, and does not, rely on them.
2. Forward branches are predicted as not taken, backward branches are
predicted as taken, no matter who says otherwise. (We have tried
several methods of state machines, caches, etc. and found out that
this simple-minded method had the best ratio of relative performance
increase vs. cost in chip area and overhead.)
--
Amos Shapir
National Semiconductor (Israel)
6 Maskit st. P.O.B. 3007, Herzlia 46104, Israel Tel. (972)52-522261
amos%nsta@nsc.com {hplabs,pyramid,sun,decwrl} 34.48'E 32.10'N
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!genrad!decvax!decwrl!nsc!nsta!instable!amos From: amos@instable.UUCP Newsgroups: comp.arch,comp.sys.nsc.32k Subject: Re: Branch prediction in the 532 Message-ID: <752@instable.UUCP> Date: Wed, 22-Apr-87 10:32:06 EST Article-I.D.: instable.752 Posted: Wed Apr 22 10:32:06 1987 Date-Received: Fri, 24-Apr-87 02:32:25 EST References: <324@dumbo.UUCP> Reply-To: amos%nsta@nsc.com (Amos Shapir) Distribution: world Organization: National Semiconductor (Israel) Ltd. Home of the 32532 Lines: 16 Summary: Someone got it wrong Hdate: 23 Nisan 5747