From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 8 Dec 2003 21:02:37 -0300 From: Ricardo Scop Reply-To: Ricardo Scop Message-ID: <6876.031208@digitel.com.br> To: Subject: Re[2]: 8270 performance In-reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Hello Jean-Denis, Monday, December 08, 2003, 6:11:30 PM, you wrote: JDB> Ricardo, JDB> Jaap-Jan, >> > I would expect the bogomips number >> > to be somewhere near the core clock >> > (like 8xx). >> >> Well, I think the numbers are pretty fair, assuming that the >> bogomips number >> reflect a certain amount of external memory accesses at 66 >> MHz external bus >> clock. JDB> It has more to do with pipelining! JDB> Hopefully, there ain't any memory access during calibration... JDB> (except, of course, when the instruction cache is disabled!) JDB> I didn't look at the documentation, but the execution of a branch probably occurs later in the pipeline of a 8260 than for the 860. It probably looses one more cycle. The calibration relies on JDB> the execution speed of function __delay (arch/ppc/kernel/misc.S), which loops on a branch instruction 'bdnz'. Ooops, I should learn to read the source code before making any assumptions. Sorry for the mistake, and many thanks for the lesson! -Scop. JDB> Regards, JDB> -------------------------------------------- JDB> Jean-Denis Boyer, Eng. JDB> M5T Centre d'Excellence en Télécoms Inc. JDB> 4283 Garlock Street JDB> Sherbrooke (Québec) JDB> J1L 2C8 CANADA JDB> (819)829-3972 x241 JDB> -------------------------------------------- ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/