From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.gnudd.com (mail2.gnudd.com [213.203.150.91]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id CDFF0DDEE7 for ; Wed, 26 Nov 2008 21:33:31 +1100 (EST) Date: Wed, 26 Nov 2008 11:20:42 +0100 From: Alessandro Rubini To: nvbolhuis@aimvalley.nl Subject: Re: too few bogoMips on MPC8313E-RDB ? Message-ID: <20081126102042.GA11397@mail.gnudd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Sender: rubini@gnudd.com In-Reply-To: <492D1CA5.2090007@aimvalley.nl> References: <492D1CA5.2090007@aimvalley.nl> Cc: linuxppc-embedded@ozlabs.org List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > This is what a linux-2.6.x reports (for the MPC8313E running at 333 MHz): > Calibrating delay loop... 83.20 BogoMIPS (lpj=166400) > > Which can't be correct. > > A MPC870 (running at 133 mhz) has ~ 131.07 BogoMIPS Actaully, one-instruction-per-clock leads to BogoMIPS = MHz. Your "loop per jiffies" value shows you make 332800 instructions per jiffy (a loop is two instructions: increment and jump). So most liker your timer tick runs at 1000 Hz but Linux is thinking it's at 250Hz (332800 * 250 = 83.20 millions). > Of course it's only a benchmark figure. No, it's not a benchmark figure. It's the metric by which udelay() is calculated. So your udelays (and mdelays) will be 4 times shorter than required, and some hardware may be misbehaving as a result. Hope this help /alessandro, who however is not runing a powerPC these times