CPU Speed when in Windows

Topic

New Reply

I have acquired a Dell Lattitude E6400 laptop with an odd problem when on AC power only, on battery it’s normal.  It has a 2.8GHz P9700 Core2 Duo CPU. Although CPU reports normal moderate speed when in BIOS setup whether AC or battery, once Win10 is loaded it’s perpetually stuck in lowest gear when on AC, the minimum 3X @ 0.59GHz and snail slow.  The Windows power settings have no effect.  I can increase the minimum all the way to 100% and still it plods along at 3X.  Unplug the AC cord and the CPU behaves like it should per the on battery settings.

I’ve updated BIOS to the latest and updated Win10 to 1909 with no change in behavior.  Anyone here encounter this issue or have some ideas?

Reply | Quote

Replies

In Power Options > Change plan settings > Change advanced power settings, have a look at “Processor power management”.  There are different settings in there for whether the PC is on battery or AC.

Windows 10 Pro 64 bit 20H2

Reply | Quote

That’s the power settings I referred to.  They have no effect on AC.

Reply | Quote

Have you tried making a new powerplan.? On the basis of starting wih the battery version that work ok for the processor?

((Apart from starting over from 0, with ac-power on))

 

* _ ... _ *

Reply | Quote

RebusCom wrote:

That’s the power settings I referred to.  They have no effect on AC.

Check High Performance settings.

Reply | Quote

I created a custom power profile by modifying the high performance one.  It acts the same as the balanced profile or a modified balanced profile.  The CPU still goes to 3X when the AC cord is plugged in, but varies depending on demand when on battery.

Reply | Quote

Are you positive you’re using the correct power cord for that laptop? If by chance you know somebody with a matching laptop try plugging their power cord in to diagnose if you’ve got either an incorrect or a defective power cord. The adapters in the power cords have voltage ratings and it’s a possibility that yours isn’t providing the proper voltage for that laptop.

Reply | Quote

I think I’ve narrowed the problem down to the Dell power supply (charger).  The BIOS setup has an optional setting to enable adapter warning messages.  With that enabled, on bootup before Windows I get a BIOS error message that the charger is only 60W instead of the supplied 90W, and therefore the laptop will reduce performance to accommodate the lower charge rate.

The Dell PS it came with appears to be the original but I see the output rating on it is 19.5V @ 3.34A, which comes to 65W, known as a PA-12 adapter.  Doing a bit of research, the Dell 90W is known as a PA-10 adapter and that must be what the laptop is expecting.  It looks like a new PS is in order.

It’s interesting the laptop doesn’t “reduce performance” while in BIOS on AC, but does when in Windows, overriding the Windows settings.

2 users thanked author for this post.

Elly, Fred

Reply | Quote