CPU Max Frequency Falls on AC only - why?

With the battery out (using AC only) system responsiveness seems slightly slower than normal.

Then I noticed (battery out/AC only) CPU Max Frequency falls to approx 54% (as indicated in Windows Task Manager's Resource Monitor) when using the High Performance Power Plan. This also happens with the other Power Plans - CPU Max Freq falls.

This makes no sense to me. Why does this happen - what possible benefit (to the laptop's power supply) does a lower CPU Max Freq make when using AC only.

And, is there any way to get CPU Max Frequency back up to 100% (for any/all Power Plans) when using AC only?

 

There are a couple of options in the BIOS you can set. I don't know the exact directory though.

 

Thank you. Will def have a look at the BIOS to see if I can tweak things a bit.

 

Maybe you aren't using an application intensive resource so it doesn't need to utilize all of the CPU's maximum frequency? Try a couple more tests and see how it goes.

 

Well, I've decoded some movies, to the PAL format, stuff like that, with the Resource Monitor open to the right of the screen, and the CPU Max Frequency never goes above 59% or so. It can go below though.

There's a blue horizontal line, a cap, at the 59% level at all times (using High Performance Power Plan) with battery out, AC on. Makes no sense to me. Why cap CPU Max Freq when connected to the power supply? Ridiculous!

With battery in, still connected to AC, perform the exact same PAL decoding, and now CPU Max Freq is 100%. It doesn't always use 100%, mind you, but it's certainly available. And it gets done faster.

It's not that big a deal to me - I was just curious more than anything else as to why this lunacy is going on.

 

Perhaps there is something wrong with the software.or u can set the bios down. and close the automatic frequency setting.

 

Some manufacturers set the CPU to throttle down when the battery is missing. The battery acts as a power reserve for the machine in case the adapter can not supply enough power to the machine (say when you are running the CPU/GPU intensive tasks). I would suggest installing the battery. You can use Power Manager to configure how much the machine charges the battery if you're trying to reduce battery wear.

 

Without the battery (i.e. AC only), the CPU doesn't run at full speed. At least that's what I saw in my X61 (w/ T7500).

 

Precisely - kinda weird though, isn't it?

As was mentioned by duffyanneal above, "some manufacturers set the CPU to throttle down when the battery is missing."

Still, I wish they wouldn't!

 

Try creating a custom power plan with the battery out, reset and the test again

 

Maybe resetting BIOS to default will help?

If not, you can create power plan like batman just stated.

Here are mine:

 

batman - Good idea. Funny, I'd never even thought of that. I will definitely do as you suggest. Appreciated!

Arkit3kt - again, thank you for your help in this thread and for taking the time to post those screen shots.

 

no this is a hardware built-in function, your not going to bypass this with bios, without the battery the cpu max will be lowered, how much depends on cpu speed, i whined and cried about this too, but there is no workaround for it that ive ever seen, the comment about the battery acting as a reservoir in intensive use seems logical, but then after playing 3hrs of an intensive game i should see my battery at least 10% discharged, ill try it and report back