Some PCs include disk cache. This is the same concept as cache, except instead of working with RAM, this works with your hard drive.

Like cache, disk cache is special "fast RAM" that stores data that the CPU uses the most. When the CPU needs data from the hard drive, it asks the disk cache first. If the disk cache has the information, the CPU gets what it needs quicker.

The disk cache reads more information from the hard drive than the CPU needs in the hopes of having it available when the CPU needs it. It also makes write operations more efficient by waiting to do the write until the CPU is not busy.