X-Authentication-Warning:	acp3bf.physik.rwth-aachen.de: broeker owned process doing -bs
Date:	Mon, 20 Mar 2000 17:53:43 +0100 (MET)
From:	Hans-Bernhard Broeker <broeker AT physik DOT rwth-aachen DOT de>
X-Sender:	broeker AT acp3bf
To:	djgpp-workers AT delorie DOT com
Subject:	Re: Unnormals???
In-Reply-To:	<Pine.SUN.3.91.1000320180609.26722H@is>
Message-ID:	<Pine.LNX.4.10.10003201749270.25247-100000@acp3bf>
MIME-Version:	1.0
Reply-To:	djgpp-workers AT delorie DOT com
Errors-To:	dj-admin AT delorie DOT com
X-Mailing-List:	djgpp-workers AT delorie DOT com
X-Unsubscribes-To:	listserv AT delorie DOT com

On Mon, 20 Mar 2000, Eli Zaretskii wrote:

> On Mon, 20 Mar 2000, Eric Rudd wrote:
> 
> > > > On my Pentium II, I found that -NaN = -NaN * -NaN; all other sign
> > > > combinations produced +NaN.
> > >
> > > This contradicts the Intel manual.  (So what else is new?)
> > 
> > I have been poring over the Intel manuals and cannot find anything about the sign
> > of a product of NaNs.  Where did you find the information?
> 
> "Intel Architecture Software Developer's Manual", v.1 "Basic 
> Architecture" (I downloaded it from their site as 24319002.pdf, but that 
> was quite a while ago), Section 7.6, Table 7-18.  The Result column only 
> mentions a real indefinite if neither of the operands is a NaN.  Your 
> case appears to be covered by the third possible combination (two QNaNs), 
> whose result should be a QNaN, i.e. either with the sign bit reset or 
> with a mantissa that doesn't fit the real indefinite description.

It's not just 'a QNaN'. You get 'the QNaN with the bigger significand'
(i.e. mantissa), according to my book. Thinking about, this seems to imply
that the sign bit of the QNaN with the (absolutely) bigger significand is
just copied as-is.

Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.

- Raw text -