How do I set the clock in linux?

The Linux kernel, as well as other open-source kernels, include a feature known as CPU frequency modulation. This feature, often known as cpufreq, gives the system administrator a variable level of control over the CPU's clock speed. The kernel includes five governors by default: conservative, ondemand, performance, powersave, and userspace. The conservative and ondemand governors adjust the clock speed depending on the CPU load, but each with different algorithms. Unlike the ondemand governor, the conservative governor doesn't jump to maximum frequency on CPU load and decreases the frequency step by step on CPU idle, but increases the frequency step by step on CPU load and jumps to lowest frequency on CPU idle. The performance, powersave and userspace governors set the clock speed statically: performance to the highest available, powersave to the lowest available, and userspace to a frequency determined and controlled by the user.