I did experience this problem with factory BIOS, but only with higher power adaptors (90W and dock adaptor).
However, since BIOS A15, everything seemed fine, for many months, on Windows 7.
A weeks back, i upgraded to Windows 10 (10.10586.218), seeing that even Dell recommends the Windows 10 upgrade.
Now, the CPU (i7-4600u) stays locked at 576Mhz on resume on battery.
The speed of processor 1 in group 0 is being limited by system firmware. The processor has been in this reduced performance state for 290 seconds since the last report.
I see this in the event log more times than i can count...
How to reproduce:
-Plug or dock the Latitude E7440
-Enter stand-by closing the lid
-Remove the power adaptor/undock
-On resume, the CPU is limited to 20% maximum CPU frequency, until you connect the power adaptor/dock the computer again.
Now, this happens on any adaptor power (65W, 90W, dock).
I tried to use BIOS A16 and A17, but these disable the SD card card reader (which i use).
Does anyone else experience this issue, or is this issue at least known and will be fixed?
During the last 1 or 2 years I have had multiple problems regarding clock speeds with my E7440 and I have tried most suggestions I found on forums. (lUpgrading/downgrading bios, reinstalling windows, different drivers, Win7,8,10, Different AC.. No docking/with docking). For the record I have the same CPU as you mention and also noticed the event logs.
Most of the time the Clock speed would get stuck at around 20% (0.78Gighz+/-). In the beginning I had the feeling I could solve it by putting the laptop into hibernation and then boot it up again. But at some point this stopped working. At that moment I started to call Dell support but they told me that they never hear of this kind of problem about the clock speed getting stuck (yeah right, the forums are full of it) and that I should first reinstall the laptop to windows 8 because they did not support windows 10 (their website clearly states that the E7440 is Windows 10 supported).
At that moment I tried a lot again to get the clock speed back to normal. For some weird reason I found out that when I hold the laptop with 2 hands and put a bit pressure on the back the clock speed JUMPS UP and back to normal. Usually this only last for a few hours after that you have to put pressure again. I know this sounds really weird but this worked for me for a while until I got sick of doing this.
So Again I called Dell and explained the pressure stuff. Of course they found it weird and again told me to reinstall, upgrade bios.. blabla… They wanted me to send the laptop to dell (I have NBD warranty) and that it could take between 1 or 2 weeks before I got It back. This was not possible for me because I need the laptop daily (slow or not) so I told them just to come over and replace the motherboard for me.
Eventually they finally agree to come over and replace the motherboard. A nice tech guy came over and replaced the motherboard and…… life was good again! The problem finally seems solved.
So to make this long story short. I believe that some motherboards of the E7440 have a problem with the soldering or something because I could temporarily solve the clock problem by putting pressure on the laptop. So when you have some clock problems just tell them to replace the motherboard. I put a lot of time in trying to solve it myself with suggestions from Dell and stuff I found on the internet but it just doesn’t work or maybe seem to work for a short while.