ReadyBoost enables NAND memory mass storage CompactFlash, SD card, and USB flash drive devices to be used as a cache between the hard drive and random access memory in an effort to increase computing performance.

Gaining the benefit of caching implies that ReadyBoost will access the flash memory for random bits of data.

[3] When a compatible device is plugged in, the Windows AutoPlay dialog offers an additional option to use the flash drive to speed up the system; an additional ReadyBoost tab is added to the drive's properties dialog where the amount of space to be used can be configured.

In Windows 7 or later with NTFS or exFAT formatting, the maximum cache size is 32 GB per device.

[13] A system with 512 MB of RAM (the minimum requirement for Windows Vista) can see significant gains from ReadyBoost.

The core idea of ReadyBoost is that a flash memory (e.g. a USB flash drive or an SSD) has a much faster seek time than a typical magnetic hard disk (less than 1 ms), allowing it to satisfy requests faster than reading files from the hard disk.