Last weekend I spent a little time working at home and I could not get over how much slower my notebook was performing. I unplugged the power adaptor (130w) to run on battery alone and my performance was back. Could this be right?! So, I downloaded a free benchmarking tool and ran a few tests. The performance running on battery alone was more than double than when using the 130 watt power adaptor.
I then began spelunking around in the BIOS to see what havoc I could bring to life. There was one setting I found to be very interesting: Intel SpeedStep. The Intel SpeedStep setting was enabled, which at first glance sounds good like enabling a turbo charger for your computer. However, disabling this setting “puts your computer in the highest performance state and prevents the Intel SpeedStep applet or native operating system driver from adjusting the processor’s performance”. Here are the results of my benchmark testing. I think most people will prefer to disable this “feature”.
Dell M4600 Performance Rating
|Power Source||SpeedStep On||SpeedStep Off||Battery Charges|
|Medium Adaptor (130w)||
No charge, No drain
|Large Adaptor (180w)||
The most obvious results show that using a power supply with less than 180 watts with SpeedStep enabled cuts the performance about 53% to a rating of 289 – that is a huge drop. With SpeedStep disabled and using the 130 watt power supply, not only does the performance resume to 100% generating a performance rating of 624; the battery does not drain at all. It doesn’t charge either, but it does charge when the computer is in a sleep state or powered off; which will likely not be an issue for most people.
One thing also worth pointing out is the best performance numbers were obtained when using the 180w power adaptor with SpeedStep enabled. It is my belief that this highest rating is only sustainable for short periods of time and does represent a sustainable performance rating.
I have chosen to disable SpeedStep. Disabling the Intel SpeedStep may not be ideal for those of you who spend a significant amount of time working unplugged (on battery); however, I was able to use my computer for 4 hours this weekend on battery alone with SpeedStep disabled. Most people using a Dell M4600 are using it as a portable workstation and will usually be plugged into a power source.
There is one benefit I can think of in keeping the Intel SpeedStep enabled. If you are using a lower wattage power adaptor (e.g., 180w), it will reduce your processor performance enough to allow the lower wattage power adaptors to charge your battery while using your computer. But that is about the only advantage I can think of.
Changing the SpeedStep setting (Dell Precision M4600):
- Reboot computer and enter BIOS by pressing F12 (on the notebook keyboard)
- Select BIOS Setup
- Performance > Intel SpeedStep
- Un-check the Enable Intel SpeedStep
- Click Apply and exit BIOS.
The tool I used for benchmarking is NavaBench.
Below is additional information about the power adaptors I use for the M4600. I needed to look this up to confirm the wattage on the power adaptors. Power P in watts (W) is equal to the current I in amps (A), times the voltage V in volts (V):
P(W) = I(A) × V(V)
Dell Power Adaptors:
|Power Adaptor||Model||Amps||x Volts||= Watts|