Sure, it's not designed for 44W by Intel. I only measured 27W maximum
when configured to 44W. It's just that the laptop is likely configured
for an overall thermal limit of 44W because it can house a MX150 with
the same cooling system (dual heat pipe). In any case, on Windows it is
not bound by 15W long term, but runs higher, averaging at about 30W from
what I read.
The thermal point I wrote the same I think. On Linux the offset is 20,
on Windows it seems higher, as it reaches 90C and more.
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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:
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
USER PID ACCESS COMMAND
/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
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
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
dmi.bios.version: N22ET31W (1.08 )
dmi.board.asset.tag: Not Available
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.product.family: ThinkPad T480s
dmi.product.version: ThinkPad T480s
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