Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!udel!haven!uvaarpa!mcnc!ecsgate!ecsvax!urjlew From: urjlew@uncecs.edu (Rostyk Lewyckyj) Newsgroups: comp.arch Subject: Re: Killer Micro II Summary: 64 bit fp is not 64 bit! Message-ID: <1990Aug29.005329.13598@uncecs.edu> Date: 29 Aug 90 00:53:29 GMT References: <527@llnl.LLNL.GOV> <603@array.UUCP> <2482@l.cc.purdue.edu> Organization: UNC Educational Computing Service Lines: 15 One detail that should not be overlooked in this discussion of fp. precision, is that the 64 bits used to represent your number is subdivided into sign + exponent + fraction. So a 64 bit fp number gives you only between 48 and 56 bits of fraction. (56 bits for the IBM 360 architecture, and I believe 48 for a CRAY and most other base 2 machines). IEEE is what? 80 bits divided up into 1+15+64 ? So it really takes 80 bit fp for 64 bits of precision. Of course you all were already taking this into account. ----------------------------------------------- Reply-To: Rostyslaw Jarema Lewyckyj urjlew@ecsvax.UUCP , urjlew@unc.bitnet or urjlew@uncvm1.acs.unc.edu (ARPA,SURA,NSF etc. internet) tel. (919)-962-6501