From: Wes Felter <wesley@felter.org>
To: dingxn@ymail.com
Cc: linux-kernel@vger.kernel.org
Subject: Re: a question about p4_clockmod module on Xeon quad core processors
Date: Thu, 29 Jan 2009 14:47:05 -0600 [thread overview]
Message-ID: <498215C9.6090208@felter.org> (raw)
In-Reply-To: <765076.76058.qm@web59913.mail.ac4.yahoo.com>
This will give you an effective speed of 250 MHz:
for cpu in 0 1 2 3; do
cpufreq-set -c $cpu -g userspace
cpufreq-set -c $cpu -u 2.0GHz
wrmsr -p $cpu 0x19A 0x12
done
0x19A is the IA32_CLOCK_MODULATION MSR and 0x12 is calculated from the
Intel 64 and IA-32 Architectures Software Developer’s Manual section
13.5.3. Legal MSR values are 0x12 (12.5% duty cycle) - 0x1E (87.5%) or
0x00 for 100%. I tested it on a quad-core Xeon and it works.
This is somewhat reckless, so use it with caution.
Wes Felter - wesley@felter.org
next prev parent reply other threads:[~2009-01-29 20:47 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-27 20:17 a question about p4_clockmod module on Xeon quad core processors Xiaoning Ding
2009-01-27 21:23 ` Arjan van de Ven
2009-01-29 16:12 ` Xiaoning Ding
2009-01-28 21:02 ` Dave Jones
2009-01-29 2:06 ` Xiaoning Ding
2009-01-29 2:45 ` Dave Jones
2009-01-29 16:32 ` Xiaoning Ding
2009-01-29 17:08 ` Dave Jones
2009-01-29 12:27 ` Michael Tokarev
2009-01-29 17:24 ` Dave Jones
2009-01-29 19:40 ` Xiaoning Ding
2009-01-29 19:54 ` Dave Jones
2009-01-28 21:05 ` Wes Felter
2009-01-29 2:11 ` Xiaoning Ding
2009-01-29 20:47 ` Wes Felter [this message]
2009-01-30 1:12 ` Xiaoning Ding
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