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

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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.

 

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RemySphere
1 Copper

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

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Same problem here, among other things like Wi-Fi card causing a blue screen then not starting up again... Had to uninstall the driver completely, download it from dell's website and reinstall it to get Internet back.

Also, the audio produces heavy static noises when I change the brightness of the screen while listening to music or so.

Also, the screen flickers at low brightness levels, not heavy yet, but if I notice it it's not good.

Also, the fans are going crazy, running almost all the time at an way too audible state.

But the MOST annoying of it all, is that a €1400 computer I received within 25days, after arguing with the worst commercial employee of all time for a "student discount' that she made clear I didn't deserve, is running at the incredible speed of 1.6GHz after unplugging the cord the first time. 

i5, 1T SSHD, 8GB RAM, 960M and Full HD display.

I'm using it since this Tuesday, as a replacement for my MacBook Pro, this is ***. I don't care about fixing the issues, this is a HIGH END COMPUTER FOLKS. Now I have to find a good competitor again.

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

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forum.notebookreview.com/.../page-48

Seems that bios 01.01.15 is out.

I can confirm speedcapping issue is gone (i7, 4k, 1tb ssd, 16gb).

Processor SST is (still) not available.

TPM still disabled.

============================

Haris163 did find out: I was just able to update the BIOS to 01.01.15 using the update driver software option from the device manager.

My reply:

Nice find, thanks for the update.

I noticed 4 firmware update:

1) system bios update (I think that was the text, since I started writing things down after I noticed their were 4 updates);

2) Intel ME firmware update;

3) Main TI PC 0

4) EC Bios

Anyone knows what 1..4 means??

Geekbench gives same results running on battery and AC, both ways peaks multicore at 3,3 Ghz and 3,5 Ghz singlecore.

Moderator
Moderator

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

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Hi Everyone,

The  01.01.15 BIOS is now live on the Support site here. Only install the update from our support site, don't force the update through Windows Update as it is only a partial update and doesn't include all the fixes that are contained in the BIOS update.

The fixes in the update include:

1. Improve Audio performance

2. Improve NVMe Battery Life

3. Fix CPU i7 CPU performance became low after AC remove and insert.

4. Enhance system Boot time

5. Fix System may saw NO Boot Device error message with NVMe storage.

6. Enhance battery mode sleep resume time too long.

Please install the BIOS and check if all the issues are resolved that you have been experiencing on the 9550

Thanks everyone for your patience while the issues were being worked on and being tested to make sure they were resolved.

Colin H
Dell | Social Outreach Services

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

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Moderator
Moderator

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

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Thanks for bringing this to our attention, I'll pass it on to our engineering team to see if they are aware of this on the system and if there is a fix for it

Colin H
Dell | Social Outreach Services

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

unlabeled
1 Copper

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

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Thanks Colin. It is otherwise a fabulous machine, I just hope Dell can address this issue soon.

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d3msd8le
2 Bronze

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

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Reporting the same problem on a new XPS 9550.  BIOS 01.00.05.

As OP mentioned, after switching to battery, CPU frequency is capped around 1.69 GHz and only way to re-enable full speed is to sleep or reboot.  Plugging in to AC does not re-enable full speed.

byunnbi
1 Copper

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

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I'm also throwing my hat into the ring to confirm the same annoyance. I too agree, this is simply unacceptable. I noticed this problem both before and after the BIOS update via provided .exe on Dell's driver download page for 15-9550.

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Moderator

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

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So we can get some more information on this issue and to try and resolve it, can you answer a few questions for me:

1. How long does it take when running on Battery for this to occur?

2. If you disable C State, Intel Speed Step or Turbo Boost does anything change?

Thanks

Colin H
Dell | Social Outreach Services

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

d3msd8le
2 Bronze

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

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>1. How long does it take when running on Battery for this to occur?

The instant you unplug, CPU downclocks (as it should).  Plugging in to AC afterwards will not bring the clock back up.  You need to sleep or reboot to get the clock back to AC speeds.  If you reboot/sleep, then the clock is instantly back at full speed when the machine wakes.

>2. If you disable C State, Intel Speed Step or Turbo Boost does anything change?

Tried them all.  Disabling C State and Turbo Boost did not solve the problem.  Turning off Speed Step has the processor running at the full speed all the time, even on battery, regardless of plugging in/out etc.  Turning off Speed Step is obviously not a realistic option for laptops.

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

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Thanks for the info.

I've passed it on and the issue is being looked at by our Engineering team

Colin H
Dell | Social Outreach Services

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

unlabeled
1 Copper

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

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I can confirm that my observations are consistent with all of d3msd8les comments.

Speed step does block the CPU from getting locked in at a lower frequency but of course isn't feasible to use for long term in a laptop due to excessive heat and fan noise.

Using 3rd party tools like ThrottleStop and manually increasing the CPU multiplier can also force the CPU frequency back but this is a hack and more or less means the CPU always run high frequency which again isn't very desirable in a laptop. In general you don't want to use a 3rd party application to try to fight what the firmware is trying to do, much better to fix the bug in the bios.

Moderator
Moderator

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

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Hi, 

So we've done some investigating into this issue and we have an engineering version of the 9550 and we couldn't replicate this particular issue. 

We have released a new revision of the 9550 BIOS <ADMIN NOTE: Broken link has been removed from this post by Dell> today. Can you please apply the BIOS update and check if it still has the CPU problem. If the problem still occurs let me know

Colin H
Dell | Social Outreach Services

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

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