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From: nmm@cl.cam.ac.uk (Nick Maclaren)
Newsgroups: comp.arch,comp.lang.fortran
Subject: Re: Quadruple-Precision Floating Point ?
Keywords: REAL*16 hardware
Message-ID: <627@scaup.cl.cam.ac.uk>
Date: 28 Dec 88 13:11:32 GMT
References: <8561@alice.UUCP> <3688@s.cc.purdue.edu> <8899@ut-emx.UUCP>
Sender: news@cl.cam.ac.uk
Reply-To: nmm@cl.cam.ac.uk (Nick Maclaren)
Organization: U of Cambridge Comp Lab, UK
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>In article <8561@alice.UUCP> wcs@alice.UUCP (Bill Stewart, usually) writes:
>>Are there any machines that implement quad-precision (128-bit) floating
>>point numbers in hardware?

Not all items reach us here, so this may have been said before.  The original
item referred to the bundled Big Blue compilers (Fortran H etc.), which have
been dead for many years.  However, I have not seen IBM mentioned, but their
compilers have supported REAL*16 for 15 years now.

All of the larger 370 series had hardware REAL*16 almost as standard,
except for division.  This has been supported by the operating system since
at least MVT release 20 and the first version of Fortran H Extended, and the
latter has simulated the instructions on machines without the hardware (by
interrupt).  There were a good many bugs in the early libraries, but I believe
that they were sorted out a long time back (we don't use REAL*16 much).

VS Fortran (their current compiler) supports REAL*16, both in hardware and
emulation, and it is available in hardware on all of their larger machines
as standard.  Hardware support for REAL*16 division came in with the operating
system MVS/XA and not with a particular item of hardware (because it is a
microcode change, not a piece of hardware).

Nick Maclaren
University of Cambridge Computer Laboratory