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From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: net.arch
Subject: Re: IBM 360 float architecture problems
Message-ID: <4006@alice.UUCP>
Date: Thu, 18-Jul-85 11:13:26 EDT
Article-I.D.: alice.4006
Posted: Thu Jul 18 11:13:26 1985
Date-Received: Sat, 20-Jul-85 06:31:13 EDT
References: <36900010@ima.UUCP>
Organization: Bell Labs, Murray Hill
Lines: 9

John Levine argues in a rather lengthy article that the IBM floating
point format loses 3 bits compared with a binary format.  This isn't
quite true; he neglects to mention the gain of two bits because the
exponent is a power of 16 rather than a power of 2.  Of course, when
compared to the VAX, the IBM format choses to realize that gain by
allowing numbers up to 7e75 rather than 1e38, but it's still a gain.

And chopped arithmetic has its advantages too.  For instance, conversion
from double to single cannot overflow, as it can on the VAX.