Date: Thu, 22 Jan 2004 11:41:48 +0000 (GMT) From: =?iso-8859-1?q?RMH?= <rmhlldr@yahoo.co.uk> To: current@freebsd.org Subject: Re: historical stuff in math(3) Message-ID: <20040122114148.16996.qmail@web25109.mail.ukl.yahoo.com>
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Peter Jeremy wrote: > > On Wed, Jan 21, 2004 at 06:41:49AM -0500, Thomas David Rivers wrote: > >> Isn't all the vax-D format related stuff math(3) getting pretty old ? > > > > It's very similar to the IBM mainframe format. So, a port > > of FreeBSD to the IBM mainframe could still use it. (The VAX > > format was just a copy of the IBM one with an extra precision bit > > thrown in every now-and-then.) > > Not really. The IBM S/360 uses base-16 whereas virtually everyone > else (including VAX) uses binary. The S/360 double precision format > has a 14-digit (56-bit) fraction (no implicit digit), a fraction sign > and a 7-bit signed exponent. The VAX-D documentation in math(3) is > totally irrelevant to the S/360. Any serious math library would need > significant re-work to handle the increased range and reduced/variable > precision. > > Someone else mentioned the Alpha - VAX-format FP is specified in > the architecture to simplify migration from the VAX. The early chips > included it in hardware - do the recent chips still include it? > All 21264 CPUs (EV6, EV67, EV68, EV68AF, EV68CB, and EV68DC) support 32-bit and 64-bit VAX F, G, and D floating-point formats, in addition to IEEE formats. You probably mean VAX-F format; it's supported fully. VAX-D has a limited support, but still available. Besides, all Alpha floating-point instructions are separated as IEEE, VAX, and independent. Thus, it's not a good idea to remove any of VAX floating-point formats from math(3). --- Regards, Rhett ________________________________________________________________________ Yahoo! Messenger - Communicate instantly..."Ping" your friends today! Download Messenger Now http://uk.messenger.yahoo.com/download/index.html
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