Recently I have seen multiple instances (fairly rarely, but nevertheless) of the newer Dell Latitude Ultrabooks (circa 2013/2014 models, E7440 and E7240 specifically) throttling CPU frequencies under exceptional power conditions (such as possibly a misbehaving AC adapter or extremely low battery condition while under load).  I haven’t confirmed the exact circumstances which lead to this behavior, but I do know of a solution.
I first noticed this when a client recently reported sluggish operation of his brand-new E7440 Ultrabook… which, of course, made little sense considering the blazingly-fast parts (SSD included) that we purchased for him.  I checked the software briefly and saw no issues which would suggest configuration problems.  However, upon opening Task Manager, under the Performance tab, the CPU frequencies were reportedly below 400 MHz permanently–which, of course, is incredibly low considering the max Turbo Boost frequency of the i5 Haswell CPU he had of 2.8 GHz.  Fortunately, I had seen this problem once before.
My theory is that it is likely related to power disruption conditions, as I have only thus far seen it happen in circumstances where an AC adapter was not providing proper voltage or where the machine was in a very low battery state while sustaining heavy CPU loads for some reason (Windows Updates, etc.).  The machine responds by throttling CPU clock rates to protect itself from possible damage, but the problem is that it never reverts from this throttled state until it is powered off and the battery is removed.
UPDATE: A new and even better solution has been found (see comments below), as some of these machines continue to suffer from the same problem even after the BIOS update has been applied. The new solution is to remove a screw underneath the keyboard, just under the “C” key (or close to it). Believe it or not, as bizarre as it sounds, this always works. I’ve tried it on dozens of systems at this point with success each time. Disassembly is relatively simple; check out Dell’s Service Manual for more info on this if you need it.
Fortunately, the solution is easy, if not a bit difficult to discover.  All that is required is a BIOS update to the latest firmware available from Dell (support.dell.com, search for your particular model).  In my most recent client’s case, an upgrade from A05 to A15 immediately corrected the problem.  It remains to be seen whether it recurs, but I do not expect it to given the last instance I saw, where we did just the same thing and the problem was permanently corrected.
Still after upgrading to BIOS A14 and later A15 the problem remains!
The only solution is always to turn machine off or reboot.
Running ThrottleStop helps.
It does appear that exposure to extreme heat or direct sunlight for extended periods of time can provoke this permathrottle behavior even on the newest firmwares for the Latitude E7440. I wonder if Dell will be issuing another update to correct that problem, as it most certainly seems to be something which a firmware update could correct.
I am on A15 and still have the problem. According to http://en.community.dell.com/support-forums/laptop/f/3518/t/19634759 I am not the only one. It happens to me when I dock/undock the computer a couple of times during the day. Restart helps.
same here – A18 and still has this problem (started 2 days ago)
Restart doesn’t help
Update:
I think it is partially solved now:
1. Before I posted this issue, I downgraded the bios (to 01) and upgraded one by one, as some users have recommended. It didn’t help.
2. Like some other users have mentioned over other forums, pressing the chassis resulted in changed clocks. I had the same issue. I disassembled the laptop and pin pointed the area and found that specific screw was (part of) the problem, probably pressing the metal plate behind the keyboard on some electrical parts. I’ve placed some thermal pads there and now it does not happen. Obviously, there is some problem with the hardware or software in this case – not sure at all it’s the MB fault.
Anyway, it seems like it repeats itself, so for anyone that reads this – you can ask if you want to know what exactly I did and where it was
Hey e,
how exactly did you do it? Which screw was the problem?
looking forward to your answer
Dear e,
can you please describe what exactly you found / did?
I do experience problems even with the newest BIOS (A20), among others similar to what Steve Schardein describes, only a lot more serious, that makes the notebook practically unusable in the summer.
Anyone else ideas / solutions / experience?
I had the exact same issue, and found the issue to be a loose power connector (in the back of the docking) to the docking station of my Dell Latitude E7470.
Plugged it properly in, and the problem went away 😀
I had the same issue with or without the dock. IT updated my laptop with the latest BIOS but it didn’t fix the issue.
However, pressing the back of the laptop chassis did, in fact, make the laptop CPU goes up again, which was suggested in the previous post. Thanks
The actual fix is to remove the battery, hold down the power for 5 seconds, reconnect the battery and tada — the laptop will not throttle down + lock to ridiculously low speeds anymore.
The solution is removing the screw located under the c-key area below the keyboard.
Hi Quintus,
Thanks for your reply!
Do you mean it’s between the keyboard and motherboard (thus, requiring removal of the board first)?
Thanks,
Steve
I got a nice link for you my friend.
I just uploaded this: https://www.youtube.com/watch?v=00xRSqyGnks&t=2s
My team and I have fixed over 400 computers.
Thanks for this. I will give it a shot the next time I come across one of these (they’re getting rarer these days, but I’m sure I’ll see it again).
Steve
Thanks very much for this fix (removing the screw behind the c). This and cmos reset got like 6 laptops (all 7440, all stuck at 0,78 or 1,67 ghz) up and running again . I couldnt use them before because they were so slow.
All were refurb btw, in one of them I found said screw already loose, so I suspect more people know about this Dell problem.
tengo un DELL LATITUDE E7440 con procesador Intel core i5 – 4310U, 8Gb de RAM y ssd de 250 GB.
he probado retirar la bateria y encenderla solo con el adaptador AC y arranco super bien, rondando los 2,9Ghz, pero luego de un minuto volvio a estancarse en 0,78GHz. Cuando presiono la parte inferior del portatil, debajo de la letra c, la frecuenci vuelve a aumentar, intentare retirar el tornillo
I experienced the same. the CPU was at 0.39 GHz.
Resolved
1. Open the back cover disconnect the battery
2. Restart the computer without the battery plugged(plug-in charger)
3. checked the speed it will reset to its native clock speed (mine was at 3.0GHz)
4. Plug the battery back on
5. Check the clock you will see its reset to native speed
to Jouk van den Berg
Its work! It is not necessary to completely remove the screw. It is enough to unscrew it a little.
Thank you very much!
There is no need to leave the screw partly in place. Jus keep it as a trophy or so. 🙂 At the office with we have jar filled with 2500 trophy’s
well i’m don’t know if my dell e6540 can fix the cpu throttle like ur e7740s is to removnig the screw under the C-key( don’t know if the e6540′ keyboard similar to ur e7740s ).
Does work with DELL E6430 CPU throttling at 30% ?
Hi,last post was 4 years ago,but i want to add my experience.
I’ve got a Dell Latitude E7240 with the same throttling problem.
In my case i can’t update BIOS because the battery is gone and the system check if battery is present to start update.
Before remove keyboard and the screw,i’ve tried a simple fix:i’ve entered the BIOS and disabled Intel speedstep. Maybe this will not work for everyone,but in my case it did.