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Path: utzoo!utgpu!jarvis.csri.toronto.edu!csri.toronto.edu!norvell
From: norvell@csri.toronto.edu (Theodore Stevens Norvell)
Subject: Re: looking for >32-bit address space [and how will C handle it
Message-ID: <8904072220.AA03632@yorkmills.csri.toronto.edu>
Summary: Really C for Cyber 180 and data sizes for mainframes.
Organization: University of Toronto, CSRI
References: <1032@myrias.UUCP> <12289@reed.UUCP> <16568@winchester.mips.COM> <16716@cup.portal.com>
Distribution: na
Date: Fri, 7 Apr 89 18:20:51 EDT

In article <16716@cup.portal.com> Tim_CDC_Roberts@cup.portal.com writes:
>In <16568@winchester.mips.COM>, mash@mips.COM (John Mashey) asks:
>
>> One interesting issue, for some ways out, is what the 64-bit model ought
>> to be be: maybe some of the mini-super and supercomputer folks can give us
>> some hints here:
>In the Control Data Cyber 180 NOS/VE C compiler, you have the following:
>
>                char      8 bits
>                short    32 bits
>                int      64 bits
>                long     64 bits
>                float    64 bits
>                double  128 bits  [See correction below]
>
>Note that this agrees with the underlying hardware; it does not make sense
>to have a 16-bit int type, because the machine doesn't do any native 16 bit
>arithmetic.
>
>I should have looked it up, but I didn't;  addresses on the Cyber 180 are
>48 bits, so I would assume that "sizeof(*int)" is 6.  
>
Not a bad assumption, but had Tim looked it up he would have found that:
	pointer to data           64 bits
	pointer to function       64 bits
This decision was made to support programs that assume pointers and integers
are the same size.  I don't know if it was the right decision or not.

Note also that double is 64 bits not 128 as Tim said.  This is because
argument passing and floating calculation are done in double in C.  I hope
Tim isn't writing any programs that rely on 128 bit doubles :-)
The forthcoming ANSI C compiler will provide long double which will
almost certainly be 128 bits.

Since C on the Cyber 180 was brought up, let me mention that a brand new
(i.e. we haven't got a lot of the bugs out yet) C compiler will soon be out.
It will provide far better compilation rates (up to 5x) and somewhat better
object code.  It will be better integrated with the NOS/VE programming
environment too (which is not to say it will be totally unusable from Unix).

Cyber 180 is a line of computers from small mainframes to almost
supercomputers.  It should not be confused with the Cyber 170 (also
NOS/VE is not NOS).  180's have byte addressing and large virtual
address spaces (8 gigabytes).

The above should in no way be interpreted as a statement belonging to
or comming from my employer.  I'm a compiler writer, not a spokesperson.
(They already fired me; I'd rather they didn't sue me too.)

Theodore Norvell
of (what's left of) Control Data Canada