BIOS BUG REPORT: XPS 15 9550, CPU Speed capped after switching from battery to AC power

I'm also on the XPS 9550. I have a slight screen flicker when running at the lowest brightness setting, both on AC and Battery. Running latest Nov 13 BIOS + Win 10 Pro. 

Since you are a windows pro user try the hyper-v disabling option.  It for no reason should be a long term fix.  I had flickering without pro which does not come with hyper-v.  The comouter has many issues. The hyper-v may be a temp fix.  Sadly I feel as though they should have produced a better product for its price.  The surface book had flcikering issues and they immediately said we know about the issue and will fix it.  Dell says oh, we have no reported claims tats most likely a fluke.  A fluke is rare...not something that is reported buy hundreds of users.

Colin/Dell, it has been weeks now since this posting. An update would be much appreciated. Is Dell working on a fix for this issue? When can we expect a new BIOS?

Hi all,

Colin is currently out of the office. In his absence, I have received the following update from our technical escalation teams:

Dell Engineering are aware of this issue and are working closely on the resolution. The fault has been replicated and we are currently debugging the failure manifestation.

Once we have further information, we will update this thread. Thank you all for your posts on this thread.

Thank you for the update, much appreciated!

Thanks John. I appreciate your update and am glad that Dell is working towards a solution. 

Hopefully they fix it.  As i said i have replaced my computer with a surface.  To many exchanges and returns.  Just could not deal with waiting for so many issues to be resolved.  Especially since most have only 30 days to exchange.  I hope that it works out for the people that have the tollerance

Same here, the XPS is going back to Dell's facilities very soon... Huh that was painful. There is so much to like about this laptop that it is very upsetting that I must return it for refund.

I have the same issue after taking the computer out of Sleep mode.

the CPU wont go above 1.6GHZ and utilize only 65%.

if i disable Intel SpeedStep the cpu runs at 2.6GHz and goes up to 100%.

Disabling Speed Step didn't do the trick for me.

Maybe my unit is just faulty. I got 3 BSODs within a week, CPU/Memory Management related. The fans are spinning all the time at an audible state, and the battery life is going nuts (Windows can't figure out how much I have left, sometimes showing me less than 1hour around 50% battery).

I noticed something else : in the software "Intel Tweaking Utility" the core speed values are wrong. I get at idle a negative frequency around -2,30GHz, maybe that could trigger bad behaviors of some power management middleware of some sort, I don't know if that's a clue or a bug from Intel's.

Curious new twist on this bug: Switching from AC->Battery->Dell PowerCompanion did NOT cause speed to be capped.  But switching from AC->Battery->AC does cause speed to be limited.

Something about how the computer detects the 130W power supply is causing the problem.

>>My xps 15 9550, 512, 16gb ram arrived last night. Experiencing the same issues. On battery I'm getting maxed out at 2.57ghz. Plugged in it was maxing at 1.6ghz until I restarted then I was able to get up to 3.1ish ghz.

Yes, that is a correct description of the bug.  Battery should be maxxed at 2.6 GHz (there is no Turbo Boost on battery).  FYI, sleeping the XPS 9550 will also re-enable full speed, you don't have to restart.

>>Haven't hit 3.5ghz even once.

That's because the Turbo Boost speed depends on how many cores are active.  With all four cores, Turbo Boost is limited to 3.1Ghz.  If only one core is active, then it can boost to 3.5 Ghz.  You can limit the number of cores being used in the BIOS, if you want to test it.

I am having the same issue with my i7-6700k 512GB 4K laptop. I have updated to the new bios from November 13th and the issue still persists with the CPU staying at 1.69 GHz despite being plugged back in.