rdmsr (from msr-tools) reads a CPU's model-specific registers, which expose low-level state that has no other interface: turbo ratio limits, thermal status, power limits, and so on. wrmsr writes them.

sudo dnf install msr-tools            # or apt-get install msr-tools
sudo modprobe msr

sudo rdmsr -a 0x1a2                   # MSR_TEMPERATURE_TARGET on many Intel CPUs, all CPUs
sudo rdmsr -p 0 -f 15:8 0x1a2         # bit field on CPU 0
sudo rdmsr -p 0 -d 0x1a2              # decimal output

Register numbers and meanings are CPU-specific (see the vendor manual; on Intel, Volume 4 of the Software Developer's Manual). wrmsr can crash or damage a system, so only use it if you know exactly what the register does. For readable output of the common ones, use turbostat.