From mboxrd@z Thu Jan 1 00:00:00 1970 From: Riccardo Vestrini Subject: is it really better speedstep-ich vs. p4-clockmod cpufreq driver? Date: Thu, 22 Jul 2004 11:28:30 +0200 Sender: linux-laptop-owner@vger.kernel.org Message-ID: <40FF88BE.2090507@sssup.it> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-laptop@vger.kernel.org it seems that speedstep-ich and acpi cpufreq driver have only two usable clock frequencies, while p4-clockmod has eight my cpu is: Intel Mobile Intel(R) Pentium(R) 4 CPU 3.06GHz stepping 09 last 2.6 kernel I tried (2.6.7) has introduced a warning while loading p4-clockmod module: p4-clockmod: P4/Xeon(TM) CPU On-Demand Clock Modulation available p4-clockmod: Warning: Pentium 4-M detected. The speedstep-ich or acpi cpufreq modules offer voltage scaling in addition of frequency scaling. You should use either one instead of p4-clockmod, if possible. so I immediatly switched to speedstep-ich discovering that: $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies 3066590 1599960 while with p4-clockmod I have: $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies 383323 766647 1149971 1533295 1916618 2299942 2683266 3066590 using acpi driver gives a message: cpufreq: CPU0 - ACPI performance management activated. cpufreq: P0: 3059 MHz, 24000 mW, 100 uS cpufreq: *P1: 1596 MHz, 12000 mW, 100 uS but: $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies 3059000 1596000 so, what driver is supposed to be better? and why speedstep-ich driver has only two frequencies? -- Riccardo Vestrini "Computers are good at following instructions, but not at reading your mind." - D. E. Knuth, The TeXbook