If a system clock runs at 100MHz, that means there are 100 million clock cycles in one second. Every action in the computer is timed by these clock cycles, and every action takes a certain number of clock cycles to perform. When processing a memory request, for example, the memory controller can report to the processor that the data requested will arrive in six clock cycles. It's possible for the CPU and other devices to run faster or slower than the system clock. Components of different speeds simply require a multiplication or division factor to synchronize them.
Many people assume that the speed of the processor is the speed of the computer.
But most of the time, the system bus and other components run at different speeds. Increasing the speed of the processor increases the overall performance of the computer. However, the processor is only one part of the computer, and it still relies on other components in a system to complete functions. Because all the information the CPU will process must be written to or read from memory, the overall performance of a system is dramatically affected by how fast information can travel between the CPU and main memory. So, faster memory technologies contribute a great deal to overall system performance.