From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juliusz Chroboczek Subject: Cpufreq: powernow-k7 weirdness Date: 06 Jul 2003 03:00:35 +0200 Sender: cpufreq-admin@www.linux.org.uk Message-ID: Mime-Version: 1.0 Return-path: Errors-To: cpufreq-admin@www.linux.org.uk List-Unsubscribe: , List-Id: List-Post: List-Help: List-Subscribe: , List-Archive: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: cpufreq@www.linux.org.uk Cc: davej@suse.de Running stock 2.5.73 (ACPI + preempt) on a Compaq Presario 711, CPU is a 950MHz mobile Duron. I'm getting unexpected timings when enabling cpufreq. On a kernel compiled without cpufreq, a CPU bound program (repeated sieve within L1 cache) gives the following, which is consistent with what I get under 2.4.18: real 0m1.729s user 0m1.725s sys 0m0.003s On a kernel with cpufreq (powernow-k7), I get the following at boot time: powernow: AMD K7 CPU detected. powernow: PowerNOW! Technology present. Can scale: frequency and voltage. powernow: Found PSB header at c00f6b30 powernow: Table version: 0x12 powernow: Flags: 0x0 (Mobile voltage regulator) powernow: Settling Time: 100 microseconds. powernow: Has 36 PST tables. (Only dumping ones relevant to this CPU). powernow: PST:25 (@c00f6cb8) powernow: cpuid: 0x771 fsb: 100 maxFID: 0xd startvid: 0xb powernow: FID: 0x4 (5.0x [500MHz]) VID: 0xe (1.300V) powernow: FID: 0x8 (7.0x [700MHz]) VID: 0xe (1.300V) powernow: FID: 0xd (9.5x [950MHz]) VID: 0xb (1.450V) However, the timings I get are roughly 10% lower than what I'd expect, namely as follows: At 950 MHz: real 0m1.932s user 0m1.930s sys 0m0.002s At 700 MHz: real 0m2.347s user 0m2.346s sys 0m0.002s At 500 MHz: real 0m3.288s user 0m3.285s sys 0m0.003s In all three cases, /proc/cpuinfo reflects the expected frequency. If there's any more testing that I can do, please let me know by e-mail. Juliusz Chroboczek P.S. I am not subscribed to the list, and would appreciate being CCd with any replies. P.P.S. /proc/cpuinfo, under a non-powerstep kernel: processor : 0 vendor_id : AuthenticAMD cpu family : 6 model : 7 model name : Mobile AMD Duron(tm) Processor stepping : 1 cpu MHz : 946.875 cache size : 64 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 1 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow bogomips : 1863.68