The described behavior with CPU thermal throtteling was confirmed by
Lenovo. The limits are higher as in Windows "DPTF" works by driver
support and enables the "desk mode". In Linux the "desk mode" is never
reached due to the lack of sensor information and the system operates in
the "lap mode" which has much lower trip temp.

See forum threat there:

The patches are not published yet for all platforms. But as T480s, many
other models e.g. X1C6 are affected too.

Background info by Lenovo:

Technical description by German  magazine in German language only:

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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 01/22/2018
  dmi.bios.vendor: LENOVO
  dmi.bios.version: N22ET31W (1.08 )
  dmi.board.asset.tag: Not Available 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:bvnLENOVO:bvrN22ET31W(1.08):bd01/22/2018:svnLENOVO:pn20L8S02D00:pvrThinkPadT480s:rvnLENOVO:rn20L8S02D00:rvrNotDefined:cvnLENOVO:ct10:cvrNone: ThinkPad T480s 20L8S02D00
  dmi.product.version: ThinkPad T480s
  dmi.sys.vendor: LENOVO

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