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2 Bronze

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

I noticed a very similar bug for a Dell Latitude posted on this forum and am shocked that Dell has not fixed these bios bugs.

I have a brand new XPS 15 9550 and I noticed that when you connect AC power after being on battery power, the CPU frequency gets capped at 1.69 GHz as opposed to the usual 3.5 GHz. The only way to fix this is to then reboot or sleep/resume the system. What is the best way to report this BIOS bug to Dell? There has to be some way to get Dell to fix the issue in a BIOS update.

I have found several other users also complaining of this same issue:

I really hope Dell fixes this issue since it is unacceptable for Dell to sell such an expensive and premium machine with a glaring firmware bug that turns your i7 performance into a Pentium level of performance.


Replies (159)
2 Iron

Has anyone had screen flcikering? I have not tested the cpu issue but do have crazy screen flickering  Also did you buy from dell or somewhere else

2 Bronze

Uninstall MS Hyper-V if you installed it and the flickering will go away.

2 Iron

I have windows home.  No huper-v.  Also how do i check for this cpu issue?



We are looking into this issue. 

I have sent a few of you friend requests as I'd like to get some more information on the issue.

If  I haven't sent you a  friend request you can PM me, but if you do please provide your service tag in the PM.


Colin H
Dell | Social Outreach Services

I'm based in the UK and available Monday to Friday 9am-5pm GMT

Not applicable

Hello, I will be postponing my laptop order untill this issue is solved. I feel it unappropriate for such a high price product. Looks like unfinished work as is.


Is Dell listening.? this is an expensive machine, and we don't want want a defective machine which runs at half the speed.

An update would be appreciated.

I am shocked to see the previous response from Dell that the Dell engineering team were unable to replicate this problem. Are they that incompetent ?

We aren't using the released version of the XPS15 - it's a pre-release engineering version. This is one of the reasons we can't replicate the issue.

We are looking into fixing the problem. I'll be keeping everyone updated until it's resolved

Colin H
Dell | Social Outreach Services

I'm based in the UK and available Monday to Friday 9am-5pm GMT

2 Bronze

So far 100% of all XPS 15s that I have observed have had this behavior and every person who has tried this on the various Dell online forums has also found it to exist. Perhaps the engineering team should use a production machine to test this.

2 Bronze

While I have the same issue described here (1.67 GHz max when switching from battery to power), I think I've found another throttling problem in a different scenario.

I've noticed that running in a "High Performance" state from battery doesn't allow the CPU to TurboBoost above 2.6 GHz. Also, the CPU clock doesn't consistently stay at 2.6 dips down to multiplier 8, (~800 Mhz) and only reaches near 2.6 GHz when the CPU is under heavy load.

In a high-performance state I don't expect the CPU to down throttle below the rated frequency, even on battery, unless the CPU gets too hot (this one runs really cool). I also expect to be able to turboboost above the rated frequency. The downside is that I'll chew through my battery pretty quickly, but that is what I'm asking the system to do with my choice of power-state.

In the very least the down-clock seems like a problem since the battery can deliver adequate power to run the CPU at 2.6 GHz under load. I've been able to TurboBoost from battery on past Core i7 laptops. My 5+ year old laptop with a Core i7-620M could boost up to the max boost speed from battery - granted this dual-core CPU has a TDP of 35W vs the 45W quad-core core i7-6700HQ.


XPS 9550

Windows 10 Pro + latest Intel chipset and thermal management drivers

1.07 BIOS (11/02/2015)

Core i7-6700HQ

16 GB of RAM

512 GB PCI-E M.2 SSD

2 Iron

Lol.  You would think that would be an obvious decision.  Who says lets not look at a product where that problem is rampant.  Lets look at one of the only laptops without that issue and fix it using that.  Very counterproductive

2 Bronze

I have the same problem. I noticed it once I tried playing Heroes of the Storm and I was really disappointed when I saw I was getting 30FPS. I opened up the task manager and saw the CPU was only running at 1.69GHZ and never went above that. Plugging it in and unplugging it does nothing. After restart CPU was running at full frequency and I was getting 60FPS (which is nice!)

But seriously, this is a big problem for a computer this expensive to have. This is a pretty major defect that I really hope gets resolved.



16GB Ram/512GB SSD


Edit: I should note I'm running the latest bios (1.07) with the most recent windows 10 update (Version 10.0.10586)

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