PC Processors

[brauliobo]

It wasn't until the latest firmware update (linux-firmware) or kernel 4.17

The system is much slower with this frequency limitation!

On Windows it still can go up to 3ghz.

~ ❯❯❯ LANG=en lscpu
Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
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:           AuthenticAMD
CPU family:          23
Model:               17
Model name:          AMD Ryzen 5 2500U with Radeon Vega Mobile Gfx
Stepping:            0
CPU MHz:             1650.764
CPU max MHz:         2000.0000
CPU min MHz:         1600.0000
BogoMIPS:            3992.70
Virtualization:      AMD-V
L1d cache:           32K
L1i cache:           64K
L2 cache:            512K
L3 cache:            4096K
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 mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good
nopl nonstop_tsc cpuid extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a m
isalignsse 3dnowprefetch osvw skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx hw_pstate sme ssbd sev ibpb vmmcall fsgsbase bmi1 avx2 smep bmi2 rdseed adx smap clflus
hopt sha_ni xsaveopt xsavec xgetbv1 xsaves clzero irperf xsaveerptr arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vml
oad vgif overflow_recov succor smca

[wahm5824 · Accepted solution]

Hello again,

zenquiorra‌ brauliobo‌

I have just discovered how to toggle boost on / off as root user without restarting.

To enable / disable boost:

# echo "1" > /sys/devices/system/cpu/cpufreq/boost
# echo "0" > /sys/devices/system/cpu/cpufreq/boost

It's good to disable boost when you want to maximise battery or GPU performance.

I find that it can lose boost after running for a while, which can now be fixed by turning it off and back on.

Kernel: Arch Linux 5.2.0

Source: https://www.kernel.org/doc/Documentation/cpu-freq/boost.txt 

Cheers,

[brauliobo]

Interesting, it seems a new feature of 5.2, as this boost option doesn't exist in 4.19

Although I cannot see it on 3.5ghz, only less than 3ghz, what is the maximum do you see?

[artform]

Yes, the 5.2 kernel has a bunch of Ryzen Laptop improvements. It should solve all of the problems that this post has brought up...FINALLY!

[wahm5824]

I believe the more generous CPB (Core Performance Boost) patch was included in kernel 5.1 (January).
New version allows boost for any Zen CPU whereas previously it was tied to specific models.

The problem can re-appear due to heavy workload (eg. compiling / gaming) with the cover closed.
Most likely the CPU overheated, throttled itself, but then doesn't re-enable boosting when things cool down.

From reading around, the actual boost performance depends on manufacturer's TDP configuration.
On my HP, it can reach 3.6 GHz for a single core, 3.3 GHz for two & 2.5 GHz for all cores. Test setup:

# echo "low" > /sys/class/drm/card0/device/power_dpm_force_performance_level
# ryzenadj --stapm-limit=25000 --fast-limit=25000 --tctl-temp=85