Use this answer at your own risk.
This answer uses a Intel(R) Core(TM) i5-10600K for examples. The register addresses should be the same for a i7-4700MQ.
Note: If your kernel is new enough, then write access to MSRs (Machine Specific Register)s will be disabled, requiring msr.allow_writes=on to be added to your /etc/default/grub command line, GRUB_CMDLINE_LINUX_DEFAULT.
Prerequisite: msr-tools, turbostat, and msr module loaded.
The MSR_TURBO_RATIO_LIMIT (1ADH) is read only if MSR_PLATFORM_INFO (0CEH) bit 28 is 0, but is read/write if bit 28 is 1.
Example method 1:
$ sudo modprobe msr
$ sudo rdmsr --bitfield 28:28 0x0ce
1
Example method 2, use turbostat to read the register and decode it myself. Also list the method 2 way for observing turbo ratios now:
$ sudo turbostat
turbostat version 21.05.04 - Len Brown <[email protected]>
...
cpu2: MSR_PLATFORM_INFO: 0x808083af1012900
...
cpu2: MSR_TURBO_RATIO_LIMIT: 0x303030303030
48 * 100.0 = 4800.0 MHz max turbo 6 active cores
48 * 100.0 = 4800.0 MHz max turbo 5 active cores
48 * 100.0 = 4800.0 MHz max turbo 4 active cores
48 * 100.0 = 4800.0 MHz max turbo 3 active cores
48 * 100.0 = 4800.0 MHz max turbo 2 active cores
48 * 100.0 = 4800.0 MHz max turbo 1 active cores
...
So, I have the ability to change my turbo ratios.
What are they currently? Method 2, turbostat is listed and decoded above, which is probably easiest. Method 1:
$ sudo rdmsr 0x1AD
303030303030
8 bites per number of active cores ratios starting with 1, or all are 48.
So say I wanted to change 6 active cores to 47, or 2FH:
$ sudo wrmsr 0x1AD 0x2f3030303030
$ sudo rdmsr 0x1AD
2f3030303030
And also check via turbostat:
$ sudo turbostat
...
cpu10: MSR_TURBO_RATIO_LIMIT: 0x2f3030303030
47 * 100.0 = 4700.0 MHz max turbo 6 active cores
48 * 100.0 = 4800.0 MHz max turbo 5 active cores
48 * 100.0 = 4800.0 MHz max turbo 4 active cores
48 * 100.0 = 4800.0 MHz max turbo 3 active cores
48 * 100.0 = 4800.0 MHz max turbo 2 active cores
48 * 100.0 = 4800.0 MHz max turbo 1 active cores
Note: Some processor models will list turbo ratios for more cores than they actually have. i5-9600K example:
cpu5: MSR_TURBO_RATIO_LIMIT: 0x2b2b2e2e2e2e2e2e
43 * 100.0 = 4300.0 MHz max turbo 8 active cores << I only have 6 cores
43 * 100.0 = 4300.0 MHz max turbo 7 active cores << I only have 6 cores
46 * 100.0 = 4600.0 MHz max turbo 6 active cores
46 * 100.0 = 4600.0 MHz max turbo 5 active cores
46 * 100.0 = 4600.0 MHz max turbo 4 active cores
46 * 100.0 = 4600.0 MHz max turbo 3 active cores
46 * 100.0 = 4600.0 MHz max turbo 2 active cores
46 * 100.0 = 4600.0 MHz max turbo 1 active cores
That information can be ignored.
