One of the key features of Time Capsule is the ability to back up a system and files wirelessly and automatically, which eliminates the need for a separate external drive to be attached. This feature requires OS X 10.5.2 Leopard or greater as it is this OS release that enables backup over a network. The backup software is Apple's Time Machine, which regularly makes images of the files that are being changed every hour, condensing backup images as they become older, to save space. Even when using an 802.11n wireless or Gigabit Ethernet connection, the initial backup of any Mac to the drive requires significant time and Apple anticipates this process takes "overnight or longer".[6] Subsequent backups will typically be quicker as they only back up the changed files. With the August 2009 release of Snow Leopard, Apple claims the initial backup will be up to two times faster. The backup disk can also be used by Windows-based computers, and the files on it can be managed by another OS such as Windows