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

Daniel Kulesz daniel.ina1 at googlemail.com
Sun May 1 15:30:56 CEST 2016

Hi Nico,

> On 01.05.2016 12:26, Daniel Kulesz via coreboot wrote:
> > Coreboot with idle=poll: 15,8W
> > Coreboot running "stress": 37,2W
> well, this is what I would expect from the specs.
> > Vendor BIOS with idle=poll: 15W
> > Vendor BIOS with intel_pstate=disabled: 10W
> > Vendor BIOS running "stress": 24,3W (!!)
> This looks suspicious. Doing some calculation:
> You are measuring at the wall plug, efficiency could be around 83%,
> which would leave 20W. Chipset, backlight and other stuff needs power as
> well, say around 8W, leaving 12W for your 25W TDP CPU???
Well, I could imagine that the PSU's efficiency is better than 83%, and maybe the CPU is just rated at 25W TDP while in fact it consumes less. Please note that the whole family of CPUs is rated at this wattage and so is the P9600 which runs at 2,66GHz and not just 2,53GHz and at a slightly higher min. voltage (but slightly lower max. voltage).

> So, before bothering yourself with the power consumption difference
> under load, I would also check the performance of coreboot vs. vendor
That's a good point and I was also thinking about this. So I just did a few measurements using "cryptsetup benchmark" (results attached). As you can see, indeed performance with the vendor BIOS is significantly lower. But why?

As I don't really need so much performance and rather would prefer better battery lifetime, the vendor BIOS' behavior would suit me better. I will try to tweak its settings a bit and see how this impacts performance and power consumption so we can get a better idea what could be causing the impact.

> > And I didn't find any documentation about how to actually extract the
> > VGA Bios part, so any hints are welcome.
> Um, if you find a way, please document ;)
As I posted, it is there, but a bit hidden in the Wiki.

I also ran a test series with the microcode updates included => no difference.

Cheers, Daniel
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