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laptop performace degrades when plugged in

M

makken

Golden Member
I'm at my wit's end with this problem.

My friend's laptop's gaming performance degrades significantly when plugged in. When on battery power, there's no issue.

I've checked the power profile settings, they are all on the same settings for both battery and AC power (high performance). I've checked the clocks on the CPU and the GPU when plugged in and on battery power, there's no change.

However, both the GPU and CPU loads drops 50% when plugging the system in (ie. Playing Darkness 2 pegs the GPU at ~60% when on battery power. As soon as I plug into AC power, the load drops to exactly 24% and remains steady there. The GPU and memory clock does not change. The same happens for the CPU.

The system is an Alienware M15x, the CPU is an i7 720QM, the GPU is an nVidia GTX 260m. Video drivers are ForceWare 301.42.

Any ideas to what may be causing this?
 
does temperature rise? have you tried changing that 'high performance' profile to match one used on battery?
 
bico said:
does temperature rise? have you tried changing that 'high performance' profile to match one used on battery?
Click to expand...

oh yeah, temp is well within normal operating range under load on both AC power and battery (under 50C). Yes, everything in the performance profile is the same on AC and battery.
 
Things you might want to try:

Try it plugged in without the battery. If it performs normally, it may be the power supply is not able to provide the full power, or maybe the driver handling the battery charging updates is broken (back in XP days, Microsoft had a bad driver which would get up to 100% CPU usage when the battery was going bad - there were even a few patches for that which did not solve the problem because there were a number of variables involved).

On old laptops the BIOS was usually able to also set different power profiles for mains vs battery-only. Most newer ones I've seen let the OS handle that, but still worth a look: never seen a profile which is max on batteries and throttled for mains but I guess it possible to set profiles up like that.

A bit tricky: normally the easiest to diagnose hardware problems vs drivers / OS etc. is too boot a liveCD usually Linux. But I'm not sure if any liveCD would have the Nvidia binary drivers on it so while you can check the CPU like that, the GPU might be harder. I guess you could install Linux to another partition. Or maybe easier and safer to a USB stick.
 
KompuKare said:
Things you might want to try:

Try it plugged in without the battery. If it performs normally, it may be the power supply is not able to provide the full power, or maybe the driver handling the battery charging updates is broken (back in XP days, Microsoft had a bad driver which would get up to 100% CPU usage when the battery was going bad - there were even a few patches for that which did not solve the problem because there were a number of variables involved).

On old laptops the BIOS was usually able to also set different power profiles for mains vs battery-only. Most newer ones I've seen let the OS handle that, but still worth a look: never seen a profile which is max on batteries and throttled for mains but I guess it possible to set profiles up like that.

A bit tricky: normally the easiest to diagnose hardware problems vs drivers / OS etc. is too boot a liveCD usually Linux. But I'm not sure if any liveCD would have the Nvidia binary drivers on it so while you can check the CPU like that, the GPU might be harder. I guess you could install Linux to another partition. Or maybe easier and safer to a USB stick.
Click to expand...

Tried it with the battery out but same issues. I checked the bios, but no power management settings there. what's the best way to create a bootable usb drive?

Edit: did some more testing and it looks like its limited to the gpu. Linpack testing on the cpu returned expected results while plugged in.
 
Last edited:
Have you tried swapping out the AC charger itself just to eliminate it as a possible source of the problem?
 
Hey guys, thanks for all the help. It looks like we found the culprit: Alienware "Stealth Mode" kept kicking in when it was plugged in. It seems to be controlled outside of software power settings (looks like the only way to toggle it is a touch sensitive button above the Fn keys).

There's no indication (beyond the GPU being throttled to 25%) of when its running either, so its somewhat annoying.

Thanks again for the suggestions.
 
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