Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!ra!uvaarpa!polaris.cv.nrao.edu!polaris.cv.nrao.edu!dwells From: dwells@fits.cx.nrao.edu (Don Wells) Newsgroups: comp.arch Subject: Re: IEEE floating point Message-ID: Date: 30 May 91 21:39:07 GMT References: <9105250030.AA08036@ucbvax.Berkeley.EDU> <1991May25.222551.16365@zoo.toronto.edu> mccalpin@perelandra.cms.udel.edu (John D. McCalpin) writes: ... The IBM HEX results are only 2-3 bits worse than IEEE, which is seldom disastrous. If this 2-3 bit difference does cause your application serious trouble, then you should be running at the next higher ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ precision on all the platforms.... ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ I disagree with this statement. The 2-3 bit difference is very nearly one whole decimal digit. You need at least one digit for truncation guard (two is better), and you want to resolve the noise (about one more digit), so if your dynamic range is 4 digits (and quite a few measurement systems are this good today), you generally have just enough digits for signal processing with IEEE, but quite possibly not enough with hex normalization. -- Donald C. Wells Associate Scientist dwells@nrao.edu National Radio Astronomy Observatory +1-804-296-0277 Edgemont Road Fax= +1-804-296-0278 Charlottesville, Virginia 22903-2475 USA 78:31.1W, 38:02.2N