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From: guy@gorodish.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: Vax 86xx FBOX decision
Message-ID: <15735@sun.uucp>
Date: Fri, 27-Mar-87 02:52:56 EST
Article-I.D.: sun.15735
Posted: Fri Mar 27 02:52:56 1987
Date-Received: Sat, 28-Mar-87 12:47:08 EST
References: <3431@cisunx.UUCP>
Sender: news@sun.uucp
Lines: 31
Summary: Floating point??????????

> DEC's response: 
> 	'all compiles would be sped up by 50%, because the link
> 	editor uses floating point to calculate virtual addresses.'
> 
> Can anyone verify this?

Script started on Thu Mar 26 23:42:58 1987
gorodish$ egrep "float|double" /arch/4.3/usr/src/bin/ld.c
				if (t >= sizeof (double))
					rnd = sizeof (double);
gorodish$ 

script done on Thu Mar 26 23:43:06 1987

Well, I don't know what DEC did to "/bin/ld" in ULTRIX, but it must
have been pretty impressive to get it to use floating point....

It *does* use *integer* modulo to compute some hash indices when
doing relocation relative to external symbols.  The following claim
was made in "Comments on 'The Case for the Reduced Instruction Set
Computer', Douglas W. Clark and William D. Strecker, ACM Computer
Architecture News, Vol. 8, No. 6, 15 October 1980, on page 38:

	The explanation of this anomaly is that the 780's Floating
	Point Accelerator speeds up the multiply in the
	multi-instruction implementation, but doesn't see INDEX at
	all.

So it is conceivable that the F-BOX on the 8650 may speed up the modulo
computation as well.  I'd still want to see this 50% speedup
first-hand before I believed it, though.