CPU: AMD A8-4500M cpupower reports 900Mhz is lowest P-state frequency. However available frequency for governor only 1.4ghz - 1.9ghz. **************************************************** [root@skittle-hp skittle]# cpupower frequency-info analyzing CPU 0: driver: acpi-cpufreq CPUs which run at the same hardware frequency: 0 CPUs which need to have their frequency coordinated by software: 0 maximum transition latency: 4.0 us. hardware limits: 1.40 GHz - 1.90 GHz available frequency steps: 1.90 GHz, 1.80 GHz, 1.70 GHz, 1.60 GHz, 1.40 GHz available cpufreq governors: ondemand, performance current policy: frequency should be within 1.40 GHz and 1.90 GHz. The governor "ondemand" may decide which speed to use within this range. current CPU frequency is 1.40 GHz (asserted by call to hardware). boost state support: Supported: yes Active: no Boost States: 2 Total States: 8 Pstate-Pb0: 2800MHz (boost state) Pstate-Pb1: 2300MHz (boost state) Pstate-P0: 1900MHz Pstate-P1: 1800MHz Pstate-P2: 1700MHz Pstate-P3: 1600MHz Pstate-P4: 1400MHz Pstate-P5: 900MHz [root@skittle-hp skittle]# cat /proc/cpuinfo processor : 0 vendor_id : AuthenticAMD cpu family : 21 model : 16 model name : AMD A8-4500M APU with Radeon(tm) HD Graphics stepping : 1 microcode : 0x6001119 cpu MHz : 1400.000 cache size : 2048 KB physical id : 0 siblings : 4 core id : 0 cpu cores : 2 apicid : 16 initial apicid : 0 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes 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 extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold bmi1 bogomips : 3794.12 TLB size : 1536 4K pages clflush size : 64 cache_alignment : 64 address sizes : 48 bits physical, 48 bits virtual power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro processor : 1 vendor_id : AuthenticAMD cpu family : 21 model : 16 model name : AMD A8-4500M APU with Radeon(tm) HD Graphics stepping : 1 microcode : 0x6001119 cpu MHz : 1400.000 cache size : 2048 KB physical id : 0 siblings : 4 core id : 1 cpu cores : 2 apicid : 17 initial apicid : 1 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes 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 extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold bmi1 bogomips : 3794.12 TLB size : 1536 4K pages clflush size : 64 cache_alignment : 64 address sizes : 48 bits physical, 48 bits virtual power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro processor : 2 vendor_id : AuthenticAMD cpu family : 21 model : 16 model name : AMD A8-4500M APU with Radeon(tm) HD Graphics stepping : 1 microcode : 0x6001119 cpu MHz : 1400.000 cache size : 2048 KB physical id : 0 siblings : 4 core id : 2 cpu cores : 2 apicid : 18 initial apicid : 2 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes 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 extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold bmi1 bogomips : 3794.12 TLB size : 1536 4K pages clflush size : 64 cache_alignment : 64 address sizes : 48 bits physical, 48 bits virtual power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro processor : 3 vendor_id : AuthenticAMD cpu family : 21 model : 16 model name : AMD A8-4500M APU with Radeon(tm) HD Graphics stepping : 1 microcode : 0x6001119 cpu MHz : 1400.000 cache size : 2048 KB physical id : 0 siblings : 4 core id : 3 cpu cores : 2 apicid : 19 initial apicid : 3 fpu : yes fpu_exception : yes cpuid level : 13 wp : yes 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 extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold bmi1 bogomips : 3794.12 TLB size : 1536 4K pages clflush size : 64 cache_alignment : 64 address sizes : 48 bits physical, 48 bits virtual power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro
please attach the output of "grep . /sys/devices/system/cpu/cpu0/cpufreq/*"
# grep . /sys/devices/system/cpu/cpu0/cpufreq/* /sys/devices/system/cpu/cpu0/cpufreq/affected_cpus:0 /sys/devices/system/cpu/cpu0/cpufreq/bios_limit:1900000 /sys/devices/system/cpu/cpu0/cpufreq/cpb:1 /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq:1900000 /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq:1900000 /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq:1400000 /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_transition_latency:4000 /sys/devices/system/cpu/cpu0/cpufreq/freqdomain_cpus:0 1 /sys/devices/system/cpu/cpu0/cpufreq/related_cpus:0 /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies:1900000 1800000 1700000 1600000 1400000 /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors:ondemand performance /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq:1900000 /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver:acpi-cpufreq /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor:performance /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq:1900000 /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq:1400000 /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed:<unsupported> **** Unfortunately I have been unable to find actual documentation that says whether the CPU actually supports 900MHz p-state
From the log, we can see that BIOS does not tell OS that 900MHZ is available. maybe you can re-check after booting with AC unplugged, but anyway, I will close this as it is not a kernel issue.