From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: To: "John David Anglin" Cc: parisc-linux@lists.parisc-linux.org Subject: Re: [parisc-linux] Branch Prediction In-Reply-To: Message from "John David Anglin" of "Sat, 26 Oct 2002 13:05:04 EDT." <200210261705.g9QH54Zx002355@hiauly1.hia.nrc.ca> References: <200210261705.g9QH54Zx002355@hiauly1.hia.nrc.ca> Date: Sat, 26 Oct 2002 19:23:03 -0600 From: Grant Grundler Message-Id: <20021027012303.7B576484E@dsl2.external.hp.com> Sender: parisc-linux-admin@lists.parisc-linux.org Errors-To: parisc-linux-admin@lists.parisc-linux.org List-Help: List-Post: List-Subscribe: , List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: "John David Anglin" wrote: > I wonder if the PA-8700 in the rp2470 has it? gsyprf11 is a 650Mhz PA8700. please try it. > I suppose it also could be an add-on chip. Think so? After reading the description I had the impression BTS has to be on chip and integrated in order to get the speed. But I'm just a SW engineer... > I am guessing but I think setting it would help on machines with > dynamic prediction hardware. There is probably a paper somewhere > on this on the HP site. > My understanding is that pc-relative branches can be predicted > from examination of the code. Indirect branches (e.g., call > returns) can't. yes. IIRC, branches forward tend to not be taken and branches backwards tend to be loops. Or something along that line. But with PBO, the static hints are better. And HPUX has a very cool "driver" called "flipper" that will flip to static hints to match performance path at run time. > I don't know how the dynamic prediction hardware > works but I would think it wouldn't be there if it didn't > improve branch prediction. yeah - I'll what I can learn about it this week. thanks, grant