# CPU freq_levels



## rft (Jul 27, 2010)

I'm using FreeBSD on the amd64 box with CPU:

```
AMD Phenom(tm) II X4 905e Processor (2500.05-MHz K8-class CPU)
```

I have a powerd turned on to save some power.
After updating operating system to 8.1-STABLE, I found that number of freq_levels reduced.

```
sysctl dev.cpu.0.freq_levels
dev.cpu.0.freq_levels: 2500/16675 1900/13640 1400/11582 800/7505
```

So, now minimal CPU frequency is 800MHz.
Before update, as I remember, minimal CPU frequency was 200MHz.

Is it possible to extend a freq_levels set?


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## User23 (Jul 27, 2010)

The last 600MHz wont save that much energy http://lists.freebsd.org/pipermail/freebsd-current/2009-May/006436.html

---

The freq levels could be a mix of different power saving mechanism.


```
acpi_perf  ACPI CPU performance states
     est        Intel Enhanced SpeedStep
     ichss      Intel SpeedStep for ICH
     powernow   AMD PowerNow! and Cool'n'Quiet for K7 and K8
     smist      Intel SMI-based SpeedStep for PIIX4
```

Maybe ACPI is missing in your configuration.

example from my host

```
# sysctl dev. | grep freq
dev.cpu.0.freq: 1600
dev.cpu.0.freq_levels: 2400/35000 2133/28000 1867/22000 1633/19250 1600/16000 1400/14000 1200/12000 1000/10000 800/8000 600/6000 400/4000 200/2000
dev.est.0.freq_settings: 2400/35000 2133/28000 1867/22000 1600/16000
dev.est.1.freq_settings: 2400/35000 2133/28000 1867/22000 1600/16000
dev.est.2.freq_settings: 2400/35000 2133/28000 1867/22000 1600/16000
dev.est.3.freq_settings: 2400/35000 2133/28000 1867/22000 1600/16000
dev.cpufreq.0.%driver: cpufreq
dev.cpufreq.0.%parent: cpu0
dev.cpufreq.1.%driver: cpufreq
dev.cpufreq.1.%parent: cpu1
dev.cpufreq.2.%driver: cpufreq
dev.cpufreq.2.%parent: cpu2
dev.cpufreq.3.%driver: cpufreq
dev.cpufreq.3.%parent: cpu3
dev.p4tcc.0.freq_settings: 10000/-1 8750/-1 7500/-1 6250/-1 5000/-1 3750/-1 2500/-1 1250/-1
dev.p4tcc.1.freq_settings: 10000/-1 8750/-1 7500/-1 6250/-1 5000/-1 3750/-1 2500/-1 1250/-1
dev.p4tcc.2.freq_settings: 10000/-1 8750/-1 7500/-1 6250/-1 5000/-1 3750/-1 2500/-1 1250/-1
dev.p4tcc.3.freq_settings: 10000/-1 8750/-1 7500/-1 6250/-1 5000/-1 3750/-1 2500/-1 1250/-1
```


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