One of the things we have lying around here is a power meter with a handy convenient watts output, so I've spent parts of yesterday and today measuring how much power my new machine uses in various circumstances.

booted, idle, X not started	98 watts
one CPU core 100% busy	132 watts
both CPU cores 100% busy	165 watts
idle at a graphical login with the ATI drivers loaded	127 watts
idle at a graphical login without the ATI drivers	98 watts
glxgears with the ATI drivers	148 watts
CPUs 100% busy, ATI drivers loaded	193 watts
CPUs 100% busy, glxgears, with the ATI drivers	200 watts

Modern graphical hardware apparently doesn't fire up all of its power-consuming stuff until you start using the 3D bits. The open source drivers for the ATI X800 graphics card in this machine don't have any 3D support, but the 'fglrx' binary ATI drivers do. (Now you know what got me started playing around with additional FC5 packages yesterday.)

I'm a bit surprised at the 30 watt difference from just enabling the 3D hardware, with no actual 3D operations going on. I believe that it sticks around even if you drop the machine into runlevel 3.

Rebooting seems to peak around 150 watts, averaging around 140 or lower. Powering up the machine averages about the same as rebooting, but has a peak of around 170 watts.

Banging on the disks makes little to no difference in the power usage, which wasn't really surprising once I thought about it. Since the disks are already spinning, the only extra load is from the read/write electronics and head seeks, and they're apparently pretty low.

(Unfortunately OpenGL stuff is not currently working without the ATI binary drivers, so I don't have power consumption figures for glxgears on the open source drivers. This may not be the fault of the binary driver packages, since I'm not sure glxgears ever worked; I didn't test it before installing the ATI binary drivers.)

I note in passing that part of the irritation with benchmarking and measurement is all of the stuff you only think of in hindsight.

Sidebar: the hardware (in summary)

The test machine has an Athlon 64 X2 4400+ with 2GB RAM in a Tyan K8E motherboard, the already mentioned ATI X800 GTO (PCIe), two 300 GB Seagate SATA drives, and a 500 watt Enermax Liberty power supply.