Thinkpads Forum

Hi never really experimented with this but is it easy/possible to Underclock/ Lower the voltage on an X220 CPU as i was looking to get less heat & better battery life if possible?
Would like to get it running more like my x200s lol

Thanks

Not sure if it'll work but IBM_ECW might be able to adjust some of what you're looking for. I'm pretty sure it was designed for the T4x series but I used it on my T61p to help bring temps down with great success. Not sure if it'll run on the X220 (or any 20 series), and if so how effectively Sandy Bridge CPUs can be undervolted... but it might be worth a shot. Otherwise RMClock would likely do the trick - though it's not free like IBM_ECW.

Windows 7 itself can underclock your X220.



Change the maximum processor state accordingly.


AFAIK undervolting is impossible in Sandy Bridge (and later) mobile CPUIs .

RealBlackStuff wrote:https://mattgadient.com/2012/05/21/sand ... ervations/

Undervolting on Sandy Bridge desktop processors is doable on BIOSes that have overclocking (and overvoltage) settings, as seen in the article
.
Laptops generally don't have this capability.

axur-delmeria wrote:AFAIK undervolting is impossible in Sandy Bridge (and later) mobile CPUIs .

Can be quite easily done with hardware modification.

nitrocaster wrote:

axur-delmeria wrote:AFAIK undervolting is impossible in Sandy Bridge (and later) mobile CPUIs .

Can be quite easily done with hardware modification.

I'll rephrase that then: "AFAIK undervolting is impossible in Sandy Bridge (and later) mobile CPUs using just software"

I have asked the same question regarding undervolting in the german thinkpad forum, unfortunately without any replies.
There seems to be no way to undervolt using software.

nitrocaster wrote:Can be quite easily done with hardware modification.

I, too, thought it should be possible. But I don't know how exactly it has to be done.
Can you give some more information on possible hardware modifications?

StefanKo wrote:Can you give some more information on possible hardware modifications?

U48 is an adjustable switching regulator that controls VCCCPUCORE. One of R_SEL[0:8] terminals (I guess, R_SEL3) is responsible for output voltage. All you have to do is to replace the resistor connected to that terminal. The tricky part is that there's no datasheet for U48 available on the internet, so it may turn into trial and error.

I already searched for a datasheet for that voltage regulator, too. Didn't find it.
So it's hard to say what can be modified. Here are some o my thoughts about this:

The vcccpucore should not be static, but adjusted to the frequency, right?
The setpoint should be given from the cougar point (VCC1R05B ??).
U48 has so many inputs, why do you think one of those resistors should change the vcccpucore?
And change the different vcccpucore linearly with the resistance, or by offset, or how?
There are some Sense signals going into U48, too. Shouldn't it try to somehow match sense and setpoint?

Maybe it is easier to change the output of U48, SPHASE1_x. There is some power driver behind that anyway.

To be honest I don't think the effort will be worth it. It'll be fun and interesting, of couse, but not worth it.

The only difference it would make is in long term high load scenarios which, generally speaking, are not that common on laptops. Most computers these days, including laptops, sit idle for more than 95% of their computing time, and the voltage is already significantly lowered for idle frequencies.

That said I too would be interested in how this could be achieved. Because, like I said, it'd be fun and interesting from an academic point of view

Many Thanks for all the replies guys. As undervolting may not be possible & certainly appears tricky to do on Sandy Bridge mob. i have gone with axur-delmeria appreciated suggestion re: the windows power setting. Changed to 70% on battery & 90% on mains.
I now seem to get quite a considerable improvement in battery life & when on mains it runs cooler. Obviously i lose some'performance' but for every day stuff so far it is negligible to me so i am quite happy .

Can you give values for your extended battery time?

Because I remember something called "Race to Idle", which means, the quicker the cpu is allowed to calculate, the earlier and longer it can sleep. See here: http://mjg59.livejournal.com/88608.html (written in an unique way

StefanKo wrote:Can you give values for your extended battery time?

Because I remember something called "Race to Idle", which means, the quicker the cpu is allowed to calculate, the earlier and longer it can sleep. See here: http://mjg59.livejournal.com/88608.html (written in an unique way

Theoretically, that should the case.
The problem is, there may be workloads (as well as quirks on the clock scaling algorithm) that can cause the CPU to get stuck at high speeds (or even Turbo clocks), to the detriment of battery life. Reducing the max clock speed is one way to alleviate it.

Stefan only tried for a couple of days & 95% has just been web browsing so i cannot really give any definite values yet but i have certainly seen an improvement in battery time. Read the article article & i guess in theory it should not happen but i am happy to keep a lower clock speed for my needs. Perhaps Azur is onto something with his explanation. Maybe you could tweak the processor setting on your machine and see if you notice any gains also?