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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:

forum.notebookreview.com/.../help-needed-from-new-xps-owners-report-serious-bios-bug-to-dell.783715

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 Bronze

Colin, first, thanks to you and your engineering team for looking into the issue.

Unfortunately the BIOS update (1.0.0.7) did not resolve the issue. I will add that I tried replicating the issue while setting the Windows Power Setting to "high performance" as well as "balanced" (all default settings)  but the CPU clock remains capped at 1.66ghz even after plugging the power adapter back in.

As OP had posted, it remains the case that either restarting or sleeping/waking the system will resume normal CPU function both on battery and on AC adapter, at least until the next time I unplug/plug the power again.

Out of curiosity, what did engineering change in BIOS 1.0.0.7 that was supposedly to solve this issue? Is it related to the power-flickering issue that the same version was supposed to address, and is the power-flickering issue other users have been reporting elsewhere related to this CPU clock problem?

2 Bronze

Colin, Thanks for looking into this. I will try the new BIOS and report back but it sounds like that probably won't do it based on the other user's report.

Are you sure the engineering team followed the proper steps to reproduce this?

This is now a widely reported with plenty of users reporting the same problem:

forum.notebookreview.com/.../help-needed-from-new-xps-owners-report-serious-bios-bug-to-dell.783715

That link also has specific steps to reproduce.

2 Bronze

i can confirm this bug as well.

here is my situation:


Config : i7/512GB/16GB RAM/4k

Steps to reproduce and observation:

  • Powerup on AC
  • CPU-Z
  • Stress CPU
  • CPU Multiplier value : 35
  • Remove AC
  • CPU Multiplier drops to 17, and then after a few secs goes up to 26 (2.57GHz)
  • Back on AC Power
  • CPU multiplier drops to 17
  • Can reproduce this behavior every time the AC power is removed/connected back.
  • System continues to be in this state till rebooted.

Btw, i am on the latest firmware/bios released today (11/13) - 1.0.0.7.

2 Bronze

I can confirm this as well.

i7/512GB/16GB RAM/4k

Bios 1.0.0.7

  • Powerup on AC
  • CPU-Z
  • Stress CPU
  • CPU Multiplier value : 35
  • Remove AC
  • CPU Multiplier drops to 17, and then after a few secs goes up to 26 (2.57GHz)
  • Back on AC Power
  • CPU multiplier drops to 17
  • Can reproduce this behavior every time the AC power is removed/connected back.
  • System continues to be in this state till rebooted.

2 Bronze

I can confirm this as well.

I've also tried the new Fast Ring Windows 10 build and it is still happening.

Config : i7/512GB/16GB RAM/4k

BIOS 1.0.0.7

2 Bronze

I can confirm - same power issue with CPU

Bios 1.07

XPS 15 9550

m.2 256 GB HD

i7

smaller battery.

2 Bronze

same issue here. I7/4k/512Gb

2 Bronze

I have the exact same issue. Performance is fine when booted up with AC on, and steps down when on battery (as expected), but when the AC is plugged back in the cpu speed stays capped at around 1.66ghz.

i7/4K/16GB RAM/1TB SSD with latest BIOS and all updates installed.

2 Bronze

I can confirm this issue.

Config: i7/16GB/4K/1TBPCIe

OS: Windows 10 Home v1155 build 10586

BIOS version: 01.00.07 (v1.0.7)

How to reproduce the issue: when AC adapter plugged in, simply unplug then plug the AC Adapter again, you will notice that the CPU muliplier is now capped to x17 (1.66Ghz) and cannot go further (normally x34).

2 Bronze

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 ?

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