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

Nico Huber nico.h at gmx.de
Sun May 1 23:41:48 CEST 2016

On 01.05.2016 15:30, Daniel Kulesz wrote:
> 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).
It's the other way around. If a sample is stable at 2.66GHz without
drawing more than 25W it's a P8800, if only 2.53GHz it's a P8700 etc.


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