Monday, February 6, 2012

Make your GeForce GT 520 (or any Nvidia) video card sip power

I recently acquired an HP ProLiant Microserver N40L to replace my old giant mid-tower RAID box. Now that FreeBSD 9.0-RELEASE has integrated ZFS v28 for several months, I decided to migrate away from OpenIndiana 151a and enjoy FreeBSD's Linux binary compatibility, more up-to-date software selection, and a broader install base.

I imported my GeForce GT 520 video card into my new ProLiant microserver. The video card can be adapted to a "low profile" PCI slot by replacing the bracket in the front of the card. I disconnected the card's fan because it was loud, annoying, and making the dreaded "my bearings are out" screeeeeeeeching noise.

The GT 520 supports two digital monitors -- one connected via HDMI, and one via DVI. After enabling the commercially supported 'nvidia' driver by adding nvidia_load="YES" to /boot/loader.conf and generating a suitable xorg.conf file by running nvidia-xconfig, I was able to run nvidia-settings and watched my card idle at 85 degrees C. My power meter measured my system's idle consumption in X11 to be 80 watts. I also noticed that the PowerMizer showed that my card was operating at the maximum performance level.

After a bit of research, I discovered how to force the card into low-power mode. I added the following boldfaced lines into my /etc/X11/xorg.conf file:

Section "Device"
  Identifier     "Device0"
  Driver         "nvidia"
  VendorName     "NVIDIA Corporation"
  BoardName      "GeForce GT 520"
  Option  "RegistryDwords" "PowerMizerEnable=0x1; PerfLevelSrc=0x2222; PowerMizerDefaultAC=0x3"
This tells the card to enable PowerMizer; 0x2222 stands for "fixed frequency on battery and on AC" (byte 0x22 is for fixed frequency, 0x33 is for adaptive frequency, MSB is for battery), and the default power profile on AC is the lowest level (0x3 is lowest power, 0x2 is medium power, and 0x1 is high power).

I rebooted, and measured my card's idle temperature at 48 degrees C and idle power consumption in X11 to be 70 watts. This is a ten-watt power savings -- and remember, I disconnected the GT 520's fan.

The GeForce GT 520 is a great choice for anyone wanting to attach one or more DVI monitors to a low-power or passively cooled workstation.

I do not recommend ATI cards because configuring them to dual-head in Solaris or BSD environments has been nothing but a headache for me.


Anonymous said...


Im running the same hardware setup as you (HP N40L + GeForce 520M), I also think the fan is way to loud!

Myself I'm running Windows 7, do you think it's safe to disconnect the fan?

At most the card will be used when watchin video using xbmc.

Thanks :)

baitisj said...

There is an equivalent NVidia tool for Windows that lets you under-clock your video card. If you search, you should be able to find it. I would suggest installing that tool and forcing your card to use the slower clock speed before disconnecting the fan.

Good luck!