Inside the Machine

The Clock

Steps 1 through 12 in the previous section don’t take an arbitrary amount of time to complete. Rather, they’re performed according to the pulse of the clock that governs every action the processor takes.

This clock pulse, which is generated by a clock generator module on the motherboard and is fed into the processor from the outside, times the functioning of the processor so that, on the DLW-1 at least, all three steps of the fetch-execute loop are completed in exactly one beat of the clock. Thus, the program in Figure 2-9, as I’ve traced its execution in the preceding section, takes exactly four clock beats to finish execution, because a new instruction is fetched on each beat of the clock.

One obvious way to speed up the execution of ...