Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!hc!beta!a!jlg
From: jlg@a.UUCP (Jim Giles)
Newsgroups: comp.arch
Subject: Yet another dumb question.
Message-ID: <554@a.UUCP>
Date: 2 Apr 88 10:51:37 GMT
Distribution: na
Organization: Los Alamos Natl Lab, Los Alamos, N.M.
Lines: 19
Keywords: Floating point, condition codes


I have dumb question (or two actually).  My copy of the IEEE floating
point standard is a draft published in 1981.  When (and where) was
the final standard published?

The draft standard implies that comparisons should be seperate instructions
(not subtracts or XORs) and that the result of a compare should be kept in
a condition code.  In particular, a comparison of two NaNs must result in
'unordered' even if the NaNs are the same.  If the result of a compare is
NOT contained in a condition code, how is the 'unordered' result held?
That is: if the compare is by a subtract (r1=r2-r3), what does r1 contain
if r2 and r3 are unordered?

Finally, if a condition code IS required, how is it to work with staged
functional units?  If I do three adds followed by a jump on the condition
code - which add sets the condition code that determines the jump.  If it's
the last one, doesn't that waste a lot of clocks?

J. Giles
Los Alamos