Windows Vista and Windows 7 computers have the unique ability to use external media, such as a USB drive, an SD card or a CompactFlash card, as a cache. What does this mean? It means that your spare SD card or hard drive can be used to serve the same function as your physical random access memory (RAM). This has a number of performance benefits for all computers that support ReadyBoost. Although ReadyBoost works with desktops and laptops, netbooks with built-in SD card slots see the most dramatic improvements in the following areas:
RAM, as you may know, is critical for multi-tasking. Typically, the more RAM you have, the faster your computer can run multiple programs at once. Your computer will first use RAM to perform caching operations, and when it runs out of RAM, it’ll begin using the hard disk instead. Hard disk drives are much slower at caching than physical RAM, and you may see significant slowdown when running several processor intensive programs at once.
ReadyBoost effectively lightens the load on your hard drive in terms of caching. Instead of having to access the hard disk drive, ReadyBoost can use your attached SD card or USB drive. Flash-based memory has much faster access speeds than a hard disk drive, particularly on laptops, where the hard drives have speeds of 5,400 RPMs or lower. That is, revolutions per minute, since in order to read and write from a hard disk, the disk has to physically spun up and read from an arm, much like a phonograph record. Flash memory, on the other hand, does not have any moving parts and can read/write much more quickly.
Solid-state memory also consumes less power than hard disk drives. While many laptops are transitioning towards solid state hard drives, the cost of a flash-based system hard drive remains prohibitively high for many. But using a ReadyBoost device is an effective happy medium that allows you to enjoy the advantages of solid state memory without spending an exorbitant sum of money. When you use an SD card as a ReadyBoost device, your physical hard drive doesn’t have to “spin up” as often for caching purposes, which helps conserve battery life.
In Windows 7, you’ll have the option to use a device as a ReadyBoost device when you first attach it. The Windows AutoPlay menu will appear, and you can choose to devote a certain amount of the drive to ReadyBoost. Windows recommends devoting one to three times the amount of physical RAM you have to ReadyBoost. Windows 7 allows you to use up to eight devices as ReadyBoost devices, meaning you could use an SD card, as well as multiple hard drives or USB thumbdrives.
You should note, however, that the performance benefit of any given ReadyBoost device relies on its access time. For example, USB 1.0 and USB 2.0 hard drives may not have as significant a benefit as a flash-based memory card or a USB 3.0 or FireWire hard drive.