Julius Plenz – Blog

New X220

I got a brand new Thinkpad X220 on thursday. I'm not much into hardware, I think it should mainly work. I have a model with 4 GB of RAM, an i7 at 2.7 GHz, UMTS preinstalled, SSD instead of a HDD and an IPS panel. It's a really nifty thing.

Paying the extra money for the SSD is totally worth it. Everything happens instantaneous. The bootup process is down to five seconds. The IPS panel is really worth it, too. ThinkPads have long been criticized for their bad displays – with the new panel at full brightness, my regular screen looks really dim and grey...

The Debian netinstall works smoothly. I haven't come around to testing all the stuff like the DisplayPort connectors, Bluetooth, UMTS, USB 3.0. But the usual stuff works out of the box.

However, there are major problems with the power management of both the graphics card and the whole system, the latter one being a regression in the recent 3.0 and 3.1 kernel series regarding ASPM. Currently I'm using the 3.1.0-1-amd64 kernel with the pcie_aspm=force boot parameter. I cannot really see a difference in power consumtion when varying this parameter, though.

A major thing, however, is re-enabling the RC6 mode of the graphics chip. This alone saves more than 4W when the computer is in an idle state. My /etc/modprobe.d/i915-kms.conf looks like this now:

options i915 modeset=1
options i915 i915_enable_rc6=1
options i915 i915_enable_fbc=1
options i915 lvds_downclock=1

Suspend/resume works fine, no flickering effects. I use the following command to find out the current power consumption:

while sleep 1; do
    awk '{printf"%.2f\n",$1/-1000}' < /sys/devices/platform/smapi/BAT0/power_now;

This requires the tp_smapi kernel module to be loaded. With full brightness (0) and while writing this blog article, the consumption is at ~12W; with medium brightness (8) it's ~8.5W; at the lowest brightness (15) it's ~8W; With the display completely turned off, it's ~6.5W. There are people who claim they only have an ~5.4 power consumption. If you have any other hints on this or if you own an X220 yourself, I'd be interested in the details.

posted 2011-12-10 tagged x220 and linux