Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!wuarchive!cs.utexas.edu!oakhill!marvin
From: marvin@oakhill.sps.mot.com (Marvin Denman)
Newsgroups: comp.arch
Subject: Re: Changing IEEE rounding modes on the fly (was Re: somthing else)
Message-ID: <1991Jun21.160606.4247@oakhill.sps.mot.com>
Date: 21 Jun 91 16:06:06 GMT
References: <9106190449.AA02871@ucbvax.Berkeley.EDU> <1991Jun19.165150.2121@shinobu.sgi.com> <3751@charon.cwi.nl>
Reply-To: marvin@bushwood.UUCP (Marvin Denman)
Organization: Motorola Inc., Austin, Texas
Lines: 20

In article <3751@charon.cwi.nl> dik@cwi.nl (Dik T. Winter) writes:
>In a previous posting I gave timings (from the manual) for the 88100, but
>apparently the fp pipelines must be flushed before a change to the fp
>control register is performed.  So I was wrong, and the 88100 does not
>meet the factor 3 criterion.  (Alas, this is not documented, and the flush
>must be programmed!)

This is not true for the 88100.  The floating point control register can be
changed on the fly with no problems.  The only flush necessary is before
reading or writing the status register.  The fp control register will only
affect instructions issued after it is modified because its information
is carried through the pipeline with it.  I'm sure because I designed it that
way.  



-- 
Marvin Denman
Motorola 88000 Design
cs.utexas.edu!oakhill!marvin