Hello everyone,

 

I'm in final testing stages of my Unraid build with the following hardware:

• Gigabyte GA-MA78LM-S2H AM3 Motherboard
  
• Sempron 140 CPU
  
• 2 GB RAM
  
• 2 x 1 TB and 2 x 500 GB hard disks
  

 

I'm able to get the power consumption to to 45w when the disks are spun down with 150w PicoPSU.

 

I wonder if my CPU is running at full 2.7 GHz at that time or if it automatically clocks itself down. I've enabled both C1E and Cool'N'Quiet in BIOS but unmenu still shows 2.7 GHz.

 

Can someone please explain whether Unraid is supposed to clock the CPU down when idle and whether that happens automatically? I did some search in the forums and it looks like it is supported but not enabled by default and some manual steps are needed which I wasn't able to find

 

Thanks!

http://lime-technology.com/forum/index.php?topic=8224.0

I saw that thread. I don't really understand what it says and what I need to do.

I saw that thread. I don't really understand what it says and what I need to do.

 

Try these commands:

 

modprobe acpi-cpufreq
modprobe powernow-k6
modprobe powernow-k7
modprobe powernow-k8

 

If any of them work, you are halfway home.  If none of them work (all return errors) then you will have to wait for the version 5.0 of unRAID.

Will try - thank you very much!

 

Here is the result:

 

Linux 2.6.32.9-unRAID.

root@unraid:~# modprobe acpi-cpufreq

FATAL: Module acpi_cpufreq not found.

root@unraid:~# modprobe powernow-k6

FATAL: Module powernow_k6 not found.

root@unraid:~# modprobe powernow-k7

FATAL: Module powernow_k7 not found.

root@unraid:~# modprobe powernow-k8

FATAL: Module powernow_k8 not found.

 

Is this expected or I did something wrong? I literally typed the commands from the Putty session, from whatever default directory it put me into.

Then your version of unRAID does not have frequency scaling for AMD chips in the kernel. 

So since I'm running pretty common to Unraid hardware and I'm running the latest production version of Unraid I'm assuming this means that it is not really working in Unraid until 5.0.

I though it had been added to at least one pre-5.0 version, but perhaps not, or perhaps it was rolled back.

 

The Intel driver is there, as others have reported using it, so it appears that the AMD driver is the one left out.

 

Look forward to 5.0-beta3.

No idea whether your board will support it, but you could look at undervolting your CPU in the BIOS.  If it's supported and it'll run stable, you should be able to reduce the power consumption considerably without losing any performance.

Are power savings considerable or it's less than 1w? Thanks!

It depends on the CPU and how well they did with power savings design.

 

For instance, the Intel i3 530 with power saving features enabled will idle 30-35 watts total for an entire system. When the CPU is going full tilt (doing Kernel compilations) power usage may hit 95-100 watts. That's substantial power savings.

There are two different things going on.

 

Consider these terms:

 

A CPU at full 100% utilization is "loaded".

 

The CPU has P states.  P0 is the default, and stock clock-speed and voltage.  This is "idle" 

 

P-states P1 and higher are reduced power states, that reduce power below "idle" by lowering clock speed and core voltage.

 

A CPU can idle at say 35 Watts, and at full load will be 94 Watts.  But the clock speed and voltage will be the constant.  This happens on the chip, and needs no OS support.

 

Under Linux, CPU frequency scaling (called Speedstep for some Intel chips, and Cool-n-quiet on AMD chips), will reduce the voltage and clock speed, for even lower power usage.  This requires OS support under Linux (although some mobos may be able to do it on their own).

 

The amount of additional power savings varies, but rarely will you get more than about 15 Watts.  AMD chips generally give better savings here than Intel chips.

 

It looks like specifically for Sempron 140 the following data exists:

- going from idle to Cool'N'Quiet saves around 4 watts

- undervolting saves around 3 watts

 

Source: http://www.techpowerup.com/reviews/AMD/Sempron_140/11.html

 

So there I go - I might as well undervolt the CPU until 5.0 comes out as savings are similar.