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

Gadfu So, after having another call with the dell tech guy, he confirmed that they have had multiple reports of in fact much slower booting after the bios update as well as being stuck at the dell logo when booting.  According to him dell is working on yet another bios update that should resolve that issue plus some other things. It will likely take at least another few weeks to be finished... Edit: He also mentioned that reinstalling Windows in Legacy BIOS Mode would resolve the issue of being stuck at the cost of not having Fast Boot.  It shouldn't be a problem if you have stock ssd in Intel RST mode. If you had this problem before, than it probably has nothing to do with the update itself. I have the same config and BIOS boot time has always been around 10 secs. On notebook review forum many users updated to 1.1.15 and only those who had non standard config (950 Pro SSD, stock SSD in AHCI etc) reported similiar problems

I have the stock SSD installed and had switched to AHCI hoping to bypass the RAID Controllers integrity check and speed up booting. This only led to random Bluescreens so I reverted back to RAID.

Switching from RAID to AHCI didnt have an impact on boot times at all - as you said, about 10 seconds. Only after BIOS 1.1.15 it skyrocketed to about 30 seconds.

The support guy was very clear, that being stuck on the dell logo at booting is a known issue and they are working on a new BIOS to fix it. I didn't mean to imply it was caused by the recent BIOS update in the first place. Sorry for the misconception. 

Did you switch to AHCI? Most likely most of your problems are related to that.

So after some tinkering I think I solved my boot time issues by resetting BIOS to BIOS Defaults (not Factory Defaults) and then moving the SSD to first place in boot sequence before Windows Boot Manager and re-enabling fast boot. Boot time is now back to 12ish seconds, which is the same time as on BIOS 1.1.07.

This still leaves me with capped CPU speed to 1.69GHz on Battery with BIOS 1.1.15.

Also when stressing the CPU, Windows logs show "the speed of processor 1 in group 0 is being limited by system firmware" for each logical core, no matter if booted on battery or pulling the plug afterwards. 

Thanks for the advice. I alread figured it out. Infact it was caused by the only Dell Application that I had installed: Dell Command | Power Manager. Regardless of the Power Profile I chose.

After removing Power Manager everything is fine. 

So after some tinkering I think I solved my boot time issues by resetting BIOS to BIOS Defaults (not Factory Defaults) and then moving the SSD to first place in boot sequence before Windows Boot Manager and re-enabling fast boot. Boot time is now back to 12ish seconds, which is the same time as on BIOS 1.1.07. This still leaves me with capped CPU speed to 1.69GHz on Battery with BIOS 1.1.15. Also when stressing the CPU, Windows logs show "the speed of processor 1 in group 0 is being limited by system firmware" for each logical core, no matter if booted on battery or pulling the plug afterwards.

Take a look at your power scheme configuration in config menu/system/energy settings. Select the Dell scheme, reset to default and try again.

I once selected the maximum saving scheme, which resulted in a slower performance.

Hi

I installed the latest bios release on 5th of Jan.

But there is a new issues.

I can not restart my laptop. Every time I restart it get stuck at dell logo and not going beyond that.

Then I press the power button until and everything goes off completely. If I press the power button again it restarts normally.

I it happens every time I restart it. 

Then I reverted back to previous bios version 1.0.7 and restart issue solved.

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I would suggest that all owners of the XPS 15 9550 (regardless of H/W options) go to this thread and read all 67 pages (at this time).  It has a plethora of info regarding issues/fixes for this line.  Just a suggestion, mind you.

forum.notebookreview.com/.../dell-xps-15-skylake-9550-owners-lounge.783377

This is .  I'm on BIOS .19 and my mulitplier doesn't go above 31 (3.10Ghz).  The CPU is rated at 3.5Ghz.  I sincerely regret spending money on this machine,  .