Cache Definition
Cache, which is pronounced “cash” (not “catch” or “cashay”), stores recently used information so that it can be quickly accessed at a later time. Computers incorporate several different types of caching in order to run more efficiently, thereby improving performance. Common types of caches include browser cache, disk cache, memory cache, and processor cache.
- Browser cache – Most web browsers cache webpage data by default. For example, when you visit a webpage, the browser may cache the HTML, images, and any CSS or JavaScript files referenced by the page. When you browse through other pages on the site that use the same images, CSS, or JavaScript, your browser will not have to re-download the files. Instead, the browser can simply load them from the cache, which is stored on your local hard drive.
- Memory cache – When an application is running, it may cache certain data in the system memory, or RAM. For example, if you are working on a video project, the video editor may load specific video clips and audio tracks from the hard drive into RAM. Since RAM can be accessed much more quickly than a hard drive, this reduces lag when importing and editing files.
- Disk cache – Most HDDs and SSDs include a small amount of RAM that serves as a disk cache. A typical disk cache for a 1 terabyte hard drive is 32 megabytes, while a 2 TB hard drive may have a 64 MB cache. This small amount of RAM can make a big difference in the drive’s performance. For example, when you open a folder with a large number of files, the references to the files may be automatically saved in the disk cache. The next time you open the folder, the list of files may load instantly instead of taking several seconds to appears.
- Processor cache – Processor caches are even smaller than disk caches. This is because a processor cache contains tiny blocks of data, such as frequently used instructions, that can be accessed quickly by the CPU. Modern processors often contain an L1 cache that is right next to the processor and an L2 cache that is slightly further away. The L1 cache is the smallest (around 64 KB), while the L2 cache may be around 2 MB in size. Some high-end processors even include an L3 cache, which is larger than the L2 cache. When a processor accesses data from a higher level caches, it may also move the data to the lower level cache for faster access next time.
Most caching is done in in the background, so you won’t even notice it is happening. In fact, the only one of the above caches that you can control is the browser cache. You can open your browser preferences to view the cache settings and alter the size of your browser cache or empty the cache if needed.