From: Ricardo Scop <scop@digitel.com.br>
To: <linuxppc-embedded@lists.linuxppc.org>
Subject: Re[2]: 8270 performance
Date: Mon, 8 Dec 2003 21:02:37 -0300 [thread overview]
Message-ID: <6876.031208@digitel.com.br> (raw)
In-Reply-To: <AB5AF73EAF23304EA1B932174137CED7030447@m5tmail.m5t.com>
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/
next prev parent reply other threads:[~2003-12-09 0:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-08 21:11 8270 performance Jean-Denis Boyer
2003-12-09 0:02 ` Ricardo Scop [this message]
2003-12-09 7:35 ` Jaap-Jan Boor
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