From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3e1162e60711160733p152bbbd5qbf29e1d52de650f4@mail.gmail.com> Date: Fri, 16 Nov 2007 07:33:38 -0800 From: "David Leimbach" To: "Fans of the OS Plan 9 from Bell Labs" <9fans@cse.psu.edu> Subject: Re: [9fans] Current status of amd64 port? In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <3e1162e60711160641y40a8ec9ejde7d348cb417876c@mail.gmail.com> Topicbox-Message-UUID: fd284226-ead2-11e9-9d60-3106f5b1d025 On Nov 16, 2007 6:46 AM, erik quanstrom wrote: > > Per your second a), performance does often improve quite a bit with 2x > > the general purpose registers. > > > > do you have some specific numbers to back up this claim? > > - erik > Not handy, but I used to build MPI applications on Opterons in 32bit mode, then build them in 64bit mode, and nearly always get a performance boost out of the 64bit. Which was the exact opposite that I'd get on PPC 32 vs 64 bit. PPC's a different animal, using 32bit instructions even when in a "64bit mode" (doesn't really have modes), some immediate memory loads can use up to 5 instructions in assembly... I didn't look much deeper than that. I know I'm not alone in this observation either. I'm sure I could google some results, but I can't currently produce any of my own (unless I can get some time to do so on Leopard, since it supports both). Dave