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#1 2019-04-29 17:11:18

Skitter
Member
Registered: 2013-09-28
Posts: 36

Unusual CPU throttling on a new Dell Inspiron 5379

[EDIT]
I guess I should've posted it in the "Laptop issues" subforum. Please move this thread if necessary.

Hi,

Recently I've bought two Dell Inspirons 5379. After running a cpu stress-test the frequencies are almost instantly throttled from 3.9GHz to 2.1GHz + the temperatures jump from ~50C to ~99C. Here's a short video presenting the problem. The issue occurs on both laptops. Is it normal for this model? Maybe the factory thermal paste is so bad it needs to be replaced right after purchase? I wouldn't be bothered by it if not the fact that the temperature jumps occur even when I'm switching tabs in chromium (not always, but often enough for me to notice). This results in short freezes which are annoying.

Additional info:

cpupower frequency-info

analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency:  Cannot determine or is not supported.
  hardware limits: 400 MHz - 4.00 GHz
  available cpufreq governors: performance powersave
  current policy: frequency should be within 400 MHz and 4.00 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency: Unable to call hardware
  current CPU frequency: 3.49 GHz (asserted by call to kernel)
  boost state support:
    Supported: yes
    Active: yes

uname -r

5.0.9-arch1-1-ARCH

lscpu

Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
Address sizes:       39 bits physical, 48 bits virtual
CPU(s):              8
On-line CPU(s) list: 0-7
Thread(s) per core:  2
Core(s) per socket:  4
Socket(s):           1
NUMA node(s):        1
Vendor ID:           GenuineIntel
CPU family:          6
Model:               142
Model name:          Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
Stepping:            10
CPU MHz:             3646.623
CPU max MHz:         4000.0000
CPU min MHz:         400.0000
BogoMIPS:            3985.00
Virtualization:      VT-x
L1d cache:           32K
L1i cache:           32K
L2 cache:            256K
L3 cache:            8192K
NUMA node0 CPU(s):   0-7
Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf tsc_known_freq pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault epb invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp flush_l1d

dmidecode -s bios-version

1.10.0 (it's the latest BIOS version for this laptop)

Last edited by Skitter (2019-04-29 17:13:35)

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#2 2019-04-29 17:52:58

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 19,740

Re: Unusual CPU throttling on a new Dell Inspiron 5379

Moving to Laptop Issues


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

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#3 2019-05-06 15:01:55

Skitter
Member
Registered: 2013-09-28
Posts: 36

Re: Unusual CPU throttling on a new Dell Inspiron 5379

It might be a problem with the CPU fan. After a few days of testing, I've come to the following conclusions:

- when the fan is controlled by the BIOS, it doesn't spin at speeds which would be appropriate for the given CPU temperature
- after executing dell-bios-fan-control 0 (dell-bios-fan-control-git) and setting PWM to 255, the fan doesn't spin at the maximum possible RPM
- the max RPM is random after each reboot. Sometimes setting PWM to 255 results in 4800, sometimes 5500, and sometimes even 6000. The maximum speed persists until the next reboot
- there is a correlation between enabling and disabling Intel Turbo Boost in the BIOS and the maximum fan speed

I have absolutely no idea why the max RPM that the fan can reach changes after each reboot. Maybe it's a problem with POST.

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