CPU Core Speed stuck at 0.80GHz Latitude e7440

For me the solution was to remove the screw below the c-key, as suggested by a few people in the comments to this post (with youtube video): http://triplescomputers.com/blog/casestudies/solution-cpu-throttling-on-dell-latitude-ultrabooks-e7440-e7240-after-power-exceptions/ As an indication: I noted that the core speed would shortly increase after hitting the bottom of the laptop on the left side (i.e. in the area below the c-key).

Hello there,

Thanks for the good guide, it really save my days.....
I have been troubleshooting for 5 days, until I saw this post. 

I removed the screw underneath the keyboard, and then the CPU throttling is gone.

I'm happy!

Worked perfectly. I work in a company with over 500 Dell E7440 and as the years went by did this issues start to show up and we contacted Dell. No one could give a good explanation to why some of our E7440 out of the blue started to act up and even send a service guy. He did the debugging and diagnostic and no of them gave error or reported an issue. So they concluded it was a defect motherboard or CPU. Unlucky for us had the warranty already ran out and and buying parts costed the same as a new laptop.

After long time looking did i finally came across this answer and a youtube video and i was a little.. Yeah..you are pulling my leg right? and i tried it and boom the CPU went up to 100% and the right clock speed like nothing was wrong.

I did notice a minor details, that was the crashes that happened afterwards. I think i solved the issue by putting a piece of tape underneath the metal plate and the motherboard. So the plate where the keyboard is attached to can't touch they motherboard.

It's bios problem. I found how to go full speed again. I go Start menu -> power -> sleep. Wait till computer sleeps. Than power up from sleep pressing power button. Thats it.

I experienced the same (Latitude 7470) the CPU was at 0.79 GHz.

Processor Speed Limited to 0.79GHz / 800MHz

Following steps resolved the issue for me
* Turn the laptop off
* Disconnect the external AC power adapter from the Laptop
* Open the back cover and disconnect/remove the battery
* Reconnect the external AC power adapter to the Laptop
* Restart the computer without the battery and press F2 to enter the BIOS
* Check the speed. It will reset to its native clock speed (mine was at 3.0 GHz)
* Exit the BIOS and allow it to boot into Windows
* Turn the Laptop off
* Reconnect the battery and back cover
* Turn the Laptop on

Removing the screw under the C key worked for me. Crazy.

Hi there,

Go to BIOS, by pressing F2 on start up , than go to Performance, and click on +. Find Option Intel SpeedStep TM, and Disable it.

By this operation CPU will be working on highest performance. However this will for sure decrease the battery state, but will solve the issue with CPU itself.

No need for removing the screw underneath C letter, or other removal interventions. 

Problem should be investigated deeper.

I also confirm that removing the P screen under the C key worked!

I have a 5+ year old latitude E7440 that was stuck at 0.78 GHz.   I first tried to reset the BIOS by unplugging and replugging the CMOS battery.    That didn’t work.   (btw - that initially caused my computer to brick.  (Solved thanks to https://www.dell.com/community/Latitude/Dell-Latitude-E7440-won-t-boot/m-p/7352541/highlight/true#M14481)

 I followed instructions from @PowderGeek and that fixed the issue.

at first my keyboard didn’t work upon reassembly.   I found that the connecting cables became unplugged while I removed and reinstalled the keyboard. They’re funky flat ribbons that snap into a connector.    I learned how to reconnect keyboard cables by consulting pics here:   Look at KeyBoard section of this link
https://www.dell.com/support/article/en-us/sln288313/dell-latitude-e7440-customer-replaceable-unit-cru-part-removal-guide?lang=en

Now my computer is fully restored!   Happy Days

Thanks to all for sharing your discoveries!

Thanks @Rizanmsm - This procedure mostly worked for me with my 2016 M3800.

I took off the back cover. Then disconnected the battery and started the computer with only the power supply connected. The clock speed was still 800 megahertz in the BIOS at that point. I then turned the computer off.

I then disconnected the power and reconnected the battery. When I connected the battery the computer started making a periodic beeping sound. It looked like it was trying to power up. I pressed the power button to turn it off.

Then I reconnected the power supply and started this system. At that point everything was fine and the clock speed showed the normal speed of around 3 GHz.

The battery trick didn't work but removing the screw under the letter C did. 

Yes, I confirm the screw remove fix works. My reaction was ?!?

I have 2 questions :

1. Who/how did this fix get discovered?

2. What is the screw used for?

As a laptop enthusiast, I am also extremely curious about this "C key screw" solution. 

I've read that people have done this hundreds of times.

Adding an update to this.  Increasing wattage to a power supply does not "necessarily" fix this issue.  I tested with a 130 watt power supply (thin profile) that had the same symptoms and I tested with a 90 watt power supply (thicker profile, more "brick" shaped) that did not have this issue.  I believe the problem is mitigated if the power supply has the ability to hold voltage for a few seconds after being unplugged by the wall.  This further points to a "timing issue" with whatever is detecting the voltage.  As long as the power supply doesn't drain off power too quickly you should be fine.  I would expect the permanent fix to be fixing the timing issue in the BIOS for low-voltage detection.

I believe I have tracked down an issue that is similar (at least for our location.)

Problem:  Dell Latitude 5510 is seen throttling CPU speeds to 0.40 GHz (viewed under Performance tab in Task Manager.)

Cause:  From what I've seen, I believe it has to do with the computer detecting a "low voltage" from the power supply and dropping the CPUs into a safe-mode setting of 400 MHz.

Testing:  I am testing a Dell Latitude 5510 with a 65 watt power supply.  I start with a powered off laptop.  I plug in the 65 watt adapter to the wall, then I plug it into the laptop.  I power up the laptop into Windows and go into Task Manager to observe the CPU speed.  It sometimes hovers around 4.0 GHz or so (Intel Core i5-10310U@1.70GHz).  If I then unplug the power supply from the wall (not from the computer), this causes a low-voltage detection on the computer (rather than a clean power removal) and the CPUs drop to 0.40 GHz.  From this point the laptop will stay at 0.40 GHz regardless of workload.  To get the laptop CPU to ramp up again, I plug the power supply back into the wall.  The CPUs come back up to normal speed.  Now if I unplug the power supply from the side of the laptop (clean power supply removal), the CPUs continue to function normally on battery.

Test #2:  I ran this same scenario, but used a 180 watt power supply instead and did not experience the CPU safe-mode of 0.40 GHz.

Conclusion:  I believe that the BIOS is attempting to detect low voltage from the power supply.  This detection method is slower than the power runoff from the 65 watt power supply when it is unplugged from power, but left plugged into the laptop.  When you use a larger power supply such as a 180 watt power supply, the BIOS has enough time to determine that it's not a voltage drop, but that it's actually the power supply has been unplugged from the wall.

I would assume the fix would either be to fix the voltage drop detection speed (or remove it altogether) from the BIOS or to use a larger power adapter to compensate for the slow voltage drop detection method in the BIOS.