Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!seas.gwu.edu!gritz From: gritz@seas.gwu.edu (Larry Gritz) Newsgroups: comp.sys.hp Subject: Re: 68040 and Floats, is this true? Message-ID: <3286@sparko.gwu.edu> Date: 10 Jun 91 15:56:57 GMT References: <1991Jun07.213219.14174@lynx.CS.ORST.EDU> Reply-To: lg@galileo.usno.navy.mil (Larry Gritz) Organization: The George Washington University, Washington D.C. Lines: 49 In article tt@euler.jyu.fi (Tapani Tarvainen) writes: >In article <1991Jun07.213219.14174@lynx.CS.ORST.EDU> curt@OCE.ORST.EDU (Curt Vandetta) writes: > > >> A couple of days ago, I read an article (Sorry I lost it) that someone >> here on the net wrote about thier experience with the 68040 upgrade on >> the HP 9000/400t. I currently have a 68040 upgrade kit sitting on my >> desking waiting for HP-UX 7.05. Is it true that the Floating Point >> performance suffers as much as the previous post indecated? I have a >> really uneasy feeling that it is true. > > >Floating Point performance suffers!? I'd say the question is how much >it improves ... our experience from the 400t -> 425t upgrade is that >floating-point intensive programs are speeded up by a factor ranging >from around two to almost seven. My only gripe is that they don't >offer a 33MHz '040 for it, like they do for the 400s (wonder if >the 400s upgrade would work in the 400t? Or just replacing the >processor and the crystal ... if it works with a 50MHz '030 >it just might work with a 50MHz '040, too ... ) >-- >Tapani Tarvainen (tarvaine@jyu.fi, tarvainen@finjyu.bitnet) I made the original post. It turns out that it's not the actual floating point calculations that take longer, it's that HP's library routines (in particular, the ones that convert float->ascii such as fprintf) use opcodes which used to be in hardware (on the 030) but are now emulated in software (very slowly). I heard many replies from people who said that NeXT had the same problem with their 040's, but just fixed the compilers and libraries. There's no reason why HP can't do the same. Also, even if this problem with the libraries is fixed, there ARE some computations which will take longer on the 040 than on the 030. Please note that some TRIG functions which were done in hardware on the 030 could not "fit" on the 040 chip, and are therefore emulated now in software. If you want more info, feel free to send me email. If you still have doubts, I'll be happy to send you a 25 line program which will illustrate the problem very clearly. -- Larry Gritz -- Larry Gritz lg@galileo.usno.navy.mil US Naval Observatory phone: 202-653-1034 Washington, DC 20392-5100 also: gritz@seas.gwu.edu