Choosing Laptop with 940m

[Fadh Firasi]

I found a laptop with 940m :
1. lenovo u41-70
2. asus A/K/X555LB
Those laptop have same spec (i5 5200, geforce 940m).

But i'm not sure because :
1. when i buy lenovo, I worried about the battery, because in some review, it has a short battery life. But it has nice performance,and thermal throttling in this laptop is not an issue I think ...

2. when i buy asus, I worried about the performance, because my friend had asus laptop (A455LD), but it's throttling when in battery mode and full performance in AC mode. i just worried this issue will persist in A/K/X555LB....

Please help me, or, for people that have those laptop, please tell your experience when you use it...

Thank's


(sorry for my bad english)

 

[1shado1]

It's pretty normal, in fact almost universal, for a laptop to throttle when on battery power alone:

"Running a high-performance GPU at full speed while on battery can damage the battery or require more power than the battery can safely supply.
High-performance mobile GPUs can require significant amounts of power to operate at full speed. The GTX 765M requires 75 W, while top-of-the-line mobile GPUs like the GTX 780M and GTX 980M can consume up to 122 W.

The GPU is not the only power-hungry part in a laptop. A modern Intel performance mobile CPU typically draws about 47 W at full power. In addition, you need to power other system components, such as the display, disk, and USB peripherals. When you add it all up, you might need anywhere from 140 W to 200 W to operate a gaming laptop under full load depending on your system configuration.

A typical battery in a gaming laptop can store about 60-80 Wh of energy. Most Li-ion batteries are not designed to be discharged faster than twice their Wh rating per hour (2C). In addition, sustained discharge at rates exceeding 1C can significantly reduce the overall service life of the battery. Continuously pulling 150 W or more from a typical 77 Wh battery is not a great idea and your battery could overheat and fail or even catch fire. While it's likely the battery's own protection circuitry would shut down the battery if overloaded or overheated, a device should never subject its battery to an unsafe load at any time during operation.

To avoid overloading the battery, the GPU will typically throttle to a lower clock speed. The GTX 780M on my personal laptop will not run faster than about 400 Mhz when on battery. Lower clock speeds reduce power consumption not only by having transistors switch less rapidly, but also by allowing lower core voltages—power consumption and heat dissipation scale with the square of voltage."

 

[velo3100]

I can't say anything about lenovos but asus are generally good. Most laptops will throttle when on battery power as they expect you to be plugged in which makes sense as the battery life is not good when the dgpu.

 

[Fadh Firasi]

"I can't say anything about lenovos but asus are generally good. Most laptops will throttle when on battery power as they expect you to be plugged in which makes sense as the battery life is not good when the dgpu."

What's the type of your ASUS laptop?

It's pretty normal, in fact almost universal, for a laptop to throttle when on battery power alone:

"Running a high-performance GPU at full speed while on battery can damage the battery or require more power than the battery can safely supply.
High-performance mobile GPUs can require significant amounts of power to operate at full speed. The GTX 765M requires 75 W, while top-of-the-line mobile GPUs like the GTX 780M and GTX 980M can consume up to 122 W.

The GPU is not the only power-hungry part in a laptop. A modern Intel performance mobile CPU typically draws about 47 W at full power. In addition, you need to power other system components, such as the display, disk, and USB peripherals. When you add it all up, you might need anywhere from 140 W to 200 W to operate a gaming laptop under full load depending on your system configuration.

A typical battery in a gaming laptop can store about 60-80 Wh of energy. Most Li-ion batteries are not designed to be discharged faster than twice their Wh rating per hour (2C). In addition, sustained discharge at rates exceeding 1C can significantly reduce the overall service life of the battery. Continuously pulling 150 W or more from a typical 77 Wh battery is not a great idea and your battery could overheat and fail or even catch fire. While it's likely the battery's own protection circuitry would shut down the battery if overloaded or overheated, a device should never subject its battery to an unsafe load at any time during operation.

To avoid overloading the battery, the GPU will typically throttle to a lower clock speed. The GTX 780M on my personal laptop will not run faster than about 400 Mhz when on battery. Lower clock speeds reduce power consumption not only by having transistors switch less rapidly, but also by allowing lower core voltages—power consumption and heat dissipation scale with the square of voltage."

But my laptops (lenovo g400, intel 2020m and radeon 8570m) and my brother laptop (asus a43sj, pentium b940 and geforce 520m) doesn't seems to throttle when on battery. Only at first my laptop get throttled caused by high temperature. both laptop doesn't seems throttling when on battery...

 

[velo3100]

Asus n series

 

[1shado1]

"I can't say anything about lenovos but asus are generally good. Most laptops will throttle when on battery power as they expect you to be plugged in which makes sense as the battery life is not good when the dgpu."

What's the type of your ASUS laptop?

It's pretty normal, in fact almost universal, for a laptop to throttle when on battery power alone:

"Running a high-performance GPU at full speed while on battery can damage the battery or require more power than the battery can safely supply.
High-performance mobile GPUs can require significant amounts of power to operate at full speed. The GTX 765M requires 75 W, while top-of-the-line mobile GPUs like the GTX 780M and GTX 980M can consume up to 122 W.

The GPU is not the only power-hungry part in a laptop. A modern Intel performance mobile CPU typically draws about 47 W at full power. In addition, you need to power other system components, such as the display, disk, and USB peripherals. When you add it all up, you might need anywhere from 140 W to 200 W to operate a gaming laptop under full load depending on your system configuration.

A typical battery in a gaming laptop can store about 60-80 Wh of energy. Most Li-ion batteries are not designed to be discharged faster than twice their Wh rating per hour (2C). In addition, sustained discharge at rates exceeding 1C can significantly reduce the overall service life of the battery. Continuously pulling 150 W or more from a typical 77 Wh battery is not a great idea and your battery could overheat and fail or even catch fire. While it's likely the battery's own protection circuitry would shut down the battery if overloaded or overheated, a device should never subject its battery to an unsafe load at any time during operation.

To avoid overloading the battery, the GPU will typically throttle to a lower clock speed. The GTX 780M on my personal laptop will not run faster than about 400 Mhz when on battery. Lower clock speeds reduce power consumption not only by having transistors switch less rapidly, but also by allowing lower core voltages—power consumption and heat dissipation scale with the square of voltage."

But my laptops (lenovo g400, intel 2020m and radeon 8570m) and my brother laptop (asus a43sj, pentium b940 and geforce 520m) doesn't seems to throttle when on battery. Only at first my laptop get throttled caused by high temperature. both laptop doesn't seems throttling when on battery...

Then perhaps throttling on battery only happens with laptops with pretty powerful graphics cards. All the ones you mention are pretty weak. It may also be brand/model specific, due to the builders wishes regarding battery longevity. I'm not really sure. I didn't write the article quoted.

Try some benchmarking tests on the other laptops you mentioned both with and without the power adapter to see if they throttle under full load when on battery or not.

 

[Jefferry Huynh]

My laptop ASUS N56VZ (i5, GT650M, 8GB) does throttle when on battery. The ASUS mentioned with OP seems pretty good and I would like to have more review of it. Can't find anything in Notebookcheck or Laptopmag though.

 

[Fadh Firasi]

"I can't say anything about lenovos but asus are generally good. Most laptops will throttle when on battery power as they expect you to be plugged in which makes sense as the battery life is not good when the dgpu."

What's the type of your ASUS laptop?

It's pretty normal, in fact almost universal, for a laptop to throttle when on battery power alone:

"Running a high-performance GPU at full speed while on battery can damage the battery or require more power than the battery can safely supply.
High-performance mobile GPUs can require significant amounts of power to operate at full speed. The GTX 765M requires 75 W, while top-of-the-line mobile GPUs like the GTX 780M and GTX 980M can consume up to 122 W.

The GPU is not the only power-hungry part in a laptop. A modern Intel performance mobile CPU typically draws about 47 W at full power. In addition, you need to power other system components, such as the display, disk, and USB peripherals. When you add it all up, you might need anywhere from 140 W to 200 W to operate a gaming laptop under full load depending on your system configuration.

A typical battery in a gaming laptop can store about 60-80 Wh of energy. Most Li-ion batteries are not designed to be discharged faster than twice their Wh rating per hour (2C). In addition, sustained discharge at rates exceeding 1C can significantly reduce the overall service life of the battery. Continuously pulling 150 W or more from a typical 77 Wh battery is not a great idea and your battery could overheat and fail or even catch fire. While it's likely the battery's own protection circuitry would shut down the battery if overloaded or overheated, a device should never subject its battery to an unsafe load at any time during operation.

To avoid overloading the battery, the GPU will typically throttle to a lower clock speed. The GTX 780M on my personal laptop will not run faster than about 400 Mhz when on battery. Lower clock speeds reduce power consumption not only by having transistors switch less rapidly, but also by allowing lower core voltages—power consumption and heat dissipation scale with the square of voltage."

But my laptops (lenovo g400, intel 2020m and radeon 8570m) and my brother laptop (asus a43sj, pentium b940 and geforce 520m) doesn't seems to throttle when on battery. Only at first my laptop get throttled caused by high temperature. both laptop doesn't seems throttling when on battery...

Then perhaps throttling on battery only happens with laptops with pretty powerful graphics cards. All the ones you mention are pretty weak. It may also be brand/model specific, due to the builders wishes regarding battery longevity. I'm not really sure. I didn't write the article quoted.

Try some benchmarking tests on the other laptops you mentioned both with and without the power adapter to see if they throttle under full load when on battery or not.

Maybe you're right...
Thank's for solution.