From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay04.roc.ny.frontiernet.net (relay04.roc.ny.frontiernet.net [66.133.131.37]) by ozlabs.org (Postfix) with ESMTP id F244567A86 for ; Fri, 28 Jan 2005 04:48:53 +1100 (EST) Message-ID: <003501c50498$fb92f720$0301a8c0@chuck2> From: "Mark Chambers" To: "Stuart Adams" , References: <41F916ED.1070705@brightstareng.com> Date: Thu, 27 Jan 2005 12:52:32 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Subject: Re: MPC5200 bogomips List-Id: Linux on Embedded PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , ----- Original Message ----- From: "Stuart Adams" To: Sent: Thursday, January 27, 2005 11:29 AM Subject: MPC5200 bogomips > > We are only seeing 263.78 bogomips on a MPC5200 running > at 396 MHz. > > Doesn't this seem way to low ?? With a 603e core I'd expect > 1 bogomip per MHz or better. > > The exact same kernel source running on an 8xx PPC gets about > 1 bogomip per MHZ and my 745 CPU board does 2 bogomips > per MHz ... the bogomip calibration code is the same for all > PPC architectures so it seem like it should be an apples-to-apples > comparison. > > -- Stuart > Ha! You almost sound like you are quoting me from when I first looked at bogomips on the 5200. Here's the story: If you drill down to where bogomips are calculated you will see that it is measuring the speed of a dbnz instruction. The calculation assumes 2 clocks per dbnz. So the 8xx comes out at 1 BogoMIP/MHz. The 5200 takes 3 clocks/dbnz in this loop, so you get .67 BogoMIP/MHz. Not to worry, it's only one specific scenario. Overall I've found the 5200 to be about 1.5 MIPS/MHz compared to 8xx 1 MIPS/MHz. Mark Chambers