Pentium M undervolting - possible to get into Dapper?

[Muffe]

I have an Acer Travelmate 3002 WTMi laptop with a Pentium M 740 1,73 GHz CPU. Previously, the fan was nearly always running (at 800 MHz), and it did create a lot of noise... The battery time was between 100 and 120 minutes depending on the system load.

A few days ago, I found an article on the Gentoo WIKI, and thought: that is something I want to test. I also found a post on this forum, about the same topic.

Today, I downloaded the newest kernel from kernel.org, applied the patch and compiled the kernel. I have now booted into my new kernel, and the fan is very rarely spinning. I would also think that the battery life is extended by 10-30 minutes, but I have not tested that myself (I haven't had time to that).

I have tried to apply this patch into the standard Dapper kernel sources (apt-get install linux-headers-2.6.15-1, but the speedstep-centrono.c file is not present, so I can't patch it.

Is it possible to get this patch integrated into to the standard Dapper kernel? The default voltage values are the official Pentium-M values, and the CPU is not automatically undervolted if you apply this patch. The undervolting has to be done manually after each boot (you can of course write a script to do it), so if you don't want to undervolt the CPU, you don't have to do anything.

Where do I post a request for integrating a patch like this into the kernel? I don't consider it to be a bug, so I dont't know where to post it... This patch would make a laptop-owners life a lot easyer...

Thanks for all replies.

[opera118]

Originally Posted by Muffe I have tried to apply this patch into the standard Dapper kernel sources (apt-get install linux-headers-2.6.15-1, but the speedstep-centrono.c file is not present, so I can't patch it.

The kernel-headers is exactly what it says - the headers. In C source code you have c-files and h-files (header files). The header files only contains a declaration of the functions used in the c files, not the actual source code.
So downloading the source from kernel.org is the right way. I do it, many people do it.

Originally Posted by Muffe Is it possible to get this patch integrated into to the standard Dapper kernel? The default voltage values are the official Pentium-M values, and the CPU is not automatically undervolted if you apply this patch. The undervolting has to be done manually after each boot (you can of course write a script to do it), so if you don't want to undervolt the CPU, you don't have to do anything.

Originally Posted by gentoo-wiki Warning: Use at your own risk. As far as I know it has been tested only on a few computers. It may very well permanently damage your CPU. I give no guarantee as to whether it will work for you. Changing the voltage of a Pentium M CPU is not recommended because it can make it run out of its specifications.

You think ubuntu would support this?
I don't think it's an ubuntu-kind of thing to do, it's rather something for the kernel to include. It has been discussed in lkml (linux kernel mailing list) I see now, and my own laptop certainly blows (pun intended). So I'll try this. Looks promising.

Originally Posted by Muffe Where do I post a request for integrating a patch like this into the kernel? I don't consider it to be a bug, so I dont't know where to post it... This patch would make a laptop-owners life a lot easyer...

You could, if you really want, send a mail to lkml (it's public afaik) and ask the kernel people about it.

I'm off for some investigation in this... I'm literally burning my fingers on parts of my laptop.

[Omer]

So you'll probably want linux-source package.

[unf]

I have a Acer Aspire 5021Wmli in windows I use rmclock to undervoltage because it is very loud at full speed 1.6Ghz. Of course cpu scaling works but still loud.

[Muffe]

Thank you. Scince the battery meter didn't work with my self-compiled kernel with sources from kernel.org, I'm now building from the ubuntu-supplied linux-sources package. I'll report the result.

[Muffe]

I have now grabbed the kernel sources with apt-get, applied the patch from Gentoo WIKI, and compiled the kernel with standad Ubuntu configuration.

The result is good. The battery meter does work (it didn't work with the standard kernel from kernel.org), and the best of all: the battery life is extended with approximeatly 25 minutes at 700 mV at 800 MHz (11,1 volt 4800 mAh battery). The fan does not spin up so often as before , and when the machine idles for a long time, the fan does not spin at all. I have made a simple bootscript that applies the voltage settings at boot, so you don't have to apply them manually after each reboot.

I think the Ubuntu developers shoud consider applying this patch into the standard Ubuntu kernel. The new users and those with normal desktop PC's won't notice any difference at all, but the more advanced laptop users who choose to undervolt their CPU, will get a more silent laptop and linger battery life without needing to recompile the kernel.

[quaddy]

hi,

i think you dont actually have to compile a whole new kernel.
keeping in mind that the kernel shipped with ubuntu makes use of modules I simply got the kernel-source with apt-get, applied the patch and only recompiled and installed the modules. ( make modules and make modules_install | maybe its prossible to only compile the centrino-speedstep-module but i dont know how, would save some time)
worked well for me but may lead to problems that i dont have any idea of

rebooting after that should do the trick ( reloading the module should also work but the module wouldn't reload because it was in use by other modules )

My personal opinion on including the patch to the shipped kernel is, that it wouldn't be a good idea because you can easily kill your CPU with this and only people who know what they're doing should work with this.

[patrickfromspain]

I don't understand something... why this undervolting? Isn't speedstep enough???

I'd like to have some more info on this... why undervoltage the cpu and not just let it run at, say, 50% of it's gigahertz?

Thanx

[shu]

I have Pentium M 1.73 and I can have it running at 800MHz (it won't go any lower). However, while running at 800Mhz it requires 900mV voltage by default and you can - thank to gentoo patch - force it to take let's say 800mV? 700mV? The lower the voltage, the longer battery life with the same cpu power.

[opera118]

I just think I love you, Muffe. Didn't even know about this whole concept.

So, since I'm using my own kernel anyway, patching it for this was simple. And it works like magic. I used windows rmclock and prime95 to stress test what lowest voltage I could get.

patrick, speedstep is not enough, on many laptops (such as mine) the fan is a nightmare, sounds like a dog barking, and the laptop can get really hot. this is because the processor runs at a rather high voltage level. This has nothing to do with frequency actually.

My cpu had this config (ignoring mid-steps)
1.6ghz: 1.356 V
0.8ghz: 0.988 V
I have successfully made it run with:
1.6ghz: 0.956 V
0.8ghz: 0.700 V

So it uses less power on full speed now, than it used to on half speed Not that I've used the battery on this machine yet, but I'm sure the battery time will improve by some tenths of minutes.

The kernel dudes really need to implement this into the mainstream kernel...