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From: lewine@cheshirecat.webo.dg.com (Donald Lewine)
Newsgroups: comp.arch
Subject: Re: Three Address vs Two Address Architectures
Message-ID: <1991May3.142835.9196@webo.dg.com>
Date: 3 May 91 14:28:35 GMT
References: <22476@shlump.nac.dec.com>
Sender: usenet@webo.dg.com (Usenet Administration)
Reply-To: uunet!dg!lewine
Organization: Data General Corporation
Lines: 23

In article <22476@shlump.nac.dec.com>, lan_csse@netrix.nac.dec.com (CSSE LAN Test Account) writes:
|> 
|> What all this boils down to is the question does anybody out
|> there have any hard numbers on this? If so, what are they and
|> how/where did you get them.  If your mail bounces please post
|> the information. I will post a summary to the net.  Please no
|> SWAGs or back of the envelope calculations on this. I can make
|> as wild a guess as the next guy.
|> 
When I was a DEC, we did extensive measurements as part of doing
the VAX architecture.  I don't have the numbers handy (it has been
16 years), however, the answer was: Do both.

Assuming that a two address instruction is smaller and faster than
a three address instruction, there are a large number of cases where
space and cycles can be saved by including both options.  

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Donald A. Lewine                (508) 870-9008 Voice
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