TDP Intel U CPU family is defined as 25w.
Please refer to:

CPU is not meant to go to 44W that is far away as Intel designed.

To allow the optimal operation and long-term reliability of Intel 
systems, the component temperature specification is the applicable Tjmax which 
defined in MSR 0x1a2h[23:16];
Tj MAX is factory calibrated and is not user configurable.
TCC Activation Offset is set in TEMPERATURE_TARGET (0x1A2) MSR,bits [29:24];
the offset value will be subtracted from the value TjMAX.
Please try it if you like overclock.

When temperature is retrieved by the processor MSR, it is the instantaneous
temperature of the given DTS.
thermal interrupt in Linux depends on reading MSR to warn the system like:
temperature above threshold
Then EC will make CPU be full speed to cool down system, when CPU temperature 
is stable like 80C, CPU can work at the defined freq.

This is designed to make system reliable to work at the standard
performance no matter with OS.

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  Significantly lower power and thermal limits on ThinkPad T480s (and
  probably others) than on Windows

Status in linux package in Ubuntu:

Bug description:
  A ThinkPad T480s under windows has a power limit of 44W, both short
  and long term, with a thermal maximum of about 93C or so. Under Linux,
  the power limits are 44W and 15W (short) or so, and the thermal limit
  is 80C, causing a significant performance loss.

  Looking at MSR and MCHBAR values, we can see that the values are
  correctly at 44W in the MSR, but the MCHBAR is set to a lower value:

  $ sudo rdmsr -a 0x610
  $ sudo /home/jak/Downloads/iotools-1.5/iotools mmio_read64 0xfed159a0

  Setting the MCHBAR to the same value as the MSR register solves the problem. 
At some point intel-rapl seems to reduce overall frequency to 600 MHz, though.

  The thermal limit is configured in MSR register 0x1a2; rdmsr -f 29:24
  -d 0x1a2 returns 20. Setting those bits to 7 increases it, resulting
  in performance comparative to Windows.

  Most of the analysis is based on the analysis in


  This applies to all bionic kernels I have tested so far, including

  Ubuntu 4.15.0-13.14-generic 4.15.10
  ApportVersion: 2.20.9-0ubuntu4
  Architecture: amd64
   /dev/snd/pcmC2D0p:   jak        5881 F...m pulseaudio
   /dev/snd/controlC2:  jak        5881 F.... pulseaudio
   /dev/snd/controlC1:  jak        5881 F.... pulseaudio
   /dev/snd/controlC0:  jak        5881 F.... pulseaudio
  CurrentDesktop: GNOME
  DistroRelease: Ubuntu 18.04
  InstallationDate: Installed on 2018-03-14 (28 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180313)
  MachineType: LENOVO 20L8S02D00
  Package: linux (not installed)
  ProcFB: 0 inteldrmfb
  ProcKernelCmdLine: root=/dev/mapper/ubuntu--vg-root ro rootflags=subvol=@ 
quiet splash vt.handoff=1
  ProcVersionSignature: Ubuntu 4.15.0-13.14-generic 4.15.10
   linux-restricted-modules-4.15.0-13-generic N/A
   linux-backports-modules-4.15.0-13-generic  N/A
   linux-firmware                             1.173
  Tags:  bionic
  Uname: Linux 4.15.0-13-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm cdrom dip kvm lpadmin lxd plugdev sambashare sudo
  _MarkForUpload: True
  dmi.bios.date: 01/22/2018
  dmi.bios.vendor: LENOVO
  dmi.bios.version: N22ET31W (1.08 )
  dmi.board.asset.tag: Not Available
  dmi.board.name: 20L8S02D00
  dmi.board.vendor: LENOVO
  dmi.board.version: Not Defined
  dmi.chassis.asset.tag: No Asset Information
  dmi.chassis.type: 10
  dmi.chassis.vendor: LENOVO
  dmi.chassis.version: None
  dmi.product.family: ThinkPad T480s
  dmi.product.name: 20L8S02D00
  dmi.product.version: ThinkPad T480s
  dmi.sys.vendor: LENOVO

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