T420 Performance with battery & without battery

[poffemre]

Hello everyone,

I have a T420. Question is ;
My laptop has better performance with battery.
Somedays, I use it without battery(with only wall adapter) and I notice that there is a performance difference between two cases. I play with all of reachable power options but no difference. I can not solve this situation.

As summary. Cases which I face(of course by human sense- without any performance grading program/ algorithm);
Battery + Wall adapter = only battery = superior performance.
Only wall adapter(without battery) = worse performance.

System Specs;
Intel 2420M
6GB(4+2) 1333 ram
HDD/ SSD gives no change.

Is there anybody to help me. Please. Thank you.

[RealBlackStuff]

Without battery the CPU slows down, that is by design.
Put the (working) battery back in and you will be fine.
Also, you probably have a 65W charger.
Replace that with a 90W one and without battery you should now also be fine (assuming you have only Intel graphics).

[poffemre]

Alright but lets think the cases by the your point of view;
1- 65w is enough battery charging + system working.
2- 65w is not enough only system working.

This sounds comes me weird. Is'nt it ?

[Thinkpad4by3]

It says it is charging but it is not. Lets add this up:

CPU: 35W
LCD: 15W
MOBO: 20W

~70W

The computer realizes this and delivers 5W of power from the battery and 65W of power from the wall. Batteries ARE NOT AC adapters. They behave in completely different ways. Some 18650s can discharge at 5 AMPS. 5Amps * 2 cells(assumes small battery) * 10.8V = A power delivery of 108W. The battery isn't charging but it is very slowly discharging covering the rest of the power need of the system, about what the system would be idling at low brightness.

[axur-delmeria]

IIRC older laptop models have a safety feature in the BIOS that limits CPU clock speeds when a 65w adapter is used on a Thinkpad without a battery installed.

I see similar behavior on my X220... but only in Windows. Linux somehow allows me to reach max clock speed without a battery installed, and the 65w adapter plugged in.

This can be confirmed by running a benchmark. In my case I use 7-zip's benchmark option.

Windows, 65w adapter, w/o battery --> around 2200 MIPS

Linux, 65w adapter, w/o battery --> around 6000 MIPS

The usual fix is to use the 90w adapter.

[TPFanatic]

You can also keep the battery in to have no problems.

[Thinkpad4by3]

IIRC older laptop models have a safety feature in the BIOS that limits CPU clock speeds when a 65w adapter is used on a Thinkpad without a battery installed.

I see similar behavior on my X220... but only in Windows. Linux somehow allows me to reach max clock speed without a battery installed, and the 65w adapter plugged in.

This can be confirmed by running a benchmark. In my case I use 7-zip's benchmark option.

Windows, 65w adapter, w/o battery --> around 2200 MIPS

Linux, 65w adapter, w/o battery --> around 6000 MIPS

The usual fix is to use the 90w adapter.

I think Linux has much higher control of what it will allow the system to do. Probably can override the BIOS safety limits. Is Windows in performance mode?

[poffemre]

I think Linux has much higher control of what it will allow the system to do. Probably can override the BIOS safety limits. Is Windows in performance mode?

Changing power mode does not change slowness(on windows 7/10).

Okey I accept plugging battery is a solution but I wonder is there alternative solution instead of changing power adapter 65w to 90w ?

Thanks for messages!

[Thinkpad4by3]

No. You can't just get power out of thin air. If you could, you wouldn't need laptops with batteries.

[poffemre]

I wanted to ask if it could be changed by manually on bios or whereever it possible.
Thank you for previous messages.

[Thinkpad4by3]

The Thinkpad BIOSes are really locked down. Highly doubt it but you could check under CONFIG and look around.