[coreboot] Lenovo X200 running Coreboot drains 3-4W more power than with Vendor BIOS

[Daniel Kulesz]

Hi,

I was wondering why my Lenovo X200 had such a short battery lifetime when running Libreboot/Coreboot, so I did a few measurements using the following hardware configuration:

X200 with P8700 CPU
8GB RAM
LED Display (yes, one of the rare ones)
OCZ Trion SSD (unused, just idling)
Wifi and WWAN removed
Battery removed
Ubuntu MATE 16.04 Live running from an USB thumb drive
No tweaking with powertop or such

I kept this configuration unchanged except for the BIOS and waited 5 minutes after booting, so the system could settle. Then I measured power consumption both at full brightness and at minimum brightness using a conventional power meter (EKM 365) which was plugged between the AC adapter and the power socket in the wall.

I obtained the following numbers:

Vendor BIOS: 7,5W (lowest) to 10W (highest)
Libreboot 20150518 (using the precompiled binary binary): 13,3W (lowest) to 16,1W (highest)
Latest Coreboot, config attached (80a3df260767a6d9ad34b61572d483579c21476c): 10,4W (lowest) to 13,4W (highest)

While Libreboot performs much worse than Coreboot, Coreboot still eats around 3W extra when compared with the vendor BIOS. In other words: Coreboot consumes around 30-40% more juice than the vendor BIOS which is a very sad result for an ultraportable notebook.

Is this a known issue? Has someone else tried the same and obtained different numbers?

Cheers, Daniel