Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!mailrus!uflorida!gatech!gitpyr!loligo!mccalpin
From: mccalpin@loligo.fsu.edu (John McCalpin)
Newsgroups: comp.arch
Subject: Re: MIPS supports 80- & 128-bit floats.
Message-ID: <345@loligo.fsu.edu>
Date: 3 Jan 89 22:14:12 GMT
References: <10452@obiwan.mips.COM> <325@loligo.fsu.edu> <13142@cup.portal.com>
Reply-To: mccalpin@loligo.cc.fsu.edu (John McCalpin)
Organization: Supercomputer Computations Research Institute
Lines: 35

In article <13142@cup.portal.com> PLS@cup.portal.com (Paul L Schauble) writes:
>mccalpin@masig1.ocean.fsu.edu writes:
>
>>There is some hesitancy in the supercomputer community to switch to the
>>IEEE format because the exponent range of 64-bit numbers is so much
>>smaller than the range currently provided by Cray and CDC/ETA formats.
>
>Now that's a curious answer. A few weeks ago I asked this group about the 
>usage of the IEEE standard. 
>According to the response, there hasn't been a new design in several years
>that used anything else. The previous comment seems to contradict that
>answer.
>  Is the IEEE standard really the thing to use in a new design? If not, what
>is?

I think that The IEEE standard is a very good choice in a new design.
It has the advantage of being vendor-independent, and is much more
reliable than most other floating-point formats.  It is rather expensive
to do correctly, and this often translates into slower speed at a fixed
price.  But for a multi-million dollar machine, the incremental cost of
getting the same speed with the IEEE format should not be prohibitive.

Almost all workstations from independent vendors use the IEEE FP formats,
though they don't always handle all the exceptions correctly.  The large
vendors (IBM, DEC, CDC) seem to have too much vested interest in old
binaries to want to change for their machines.  I do hear from occasionally
reliable sources in CDC that the next ETA machine will use the IEEE formats.

Of course, having the same FP format is only part of portability.  The next
level of headache involves incompatibility of record types in the files
containing these binary numbers...

John D. McCalpin
mccalpin@masig1.ocean.fsu.edu
mccalpin@fsu	(BITNET or MFENET)