Editing Parallel ATA (section)

=== Interface size limitations ===
The first drive interface used 22-bit addressing mode which resulted in a maximum drive capacity of two gigabytes. Later, the first formalized ATA specification used a 28-bit addressing mode through [[LBA28]], allowing for the addressing of 2<sup>28</sup> ({{val|268435456}}) sectors (blocks) of 512 bytes each, resulting in a maximum capacity of 128&nbsp;[[Gibibyte|GiB]] (137&nbsp;[[Gigabyte|GB]]).

ATA-6 introduced 48-bit addressing, increasing the limit to 128 [[Pebibyte|PiB]] (144 [[Petabyte|PB]]). As a consequence, any ATA drive of capacity larger than about 137&nbsp;GB must be an ATA-6 or later drive. Connecting such a drive to a host with an ATA-5 or earlier interface will limit the usable capacity to the maximum of the interface.

Some operating systems, including [[Windows XP]] pre-SP1, and [[Windows 2000]] pre-SP3, disable [[LBA48]] by default, requiring the user to take extra steps to use the entire capacity of an ATA drive larger than about 137 gigabytes.<ref>{{Cite web|url=http://www.48bitlba.com/enablebiglba.htm |title=EnableBigLba Registry Setting in Windows 2000 and XP |author=FryeWare |year=2005 |access-date=2011-12-29}} The setting is <code>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\atapi\Parameters\EnableBigLba = 1</code>.</ref>

Older operating systems, such as [[Windows 98]], do not support 48-bit LBA at all. However, members of the third-party group MSFN<ref>{{Cite web|title=Enable48BitLBA - Break the 137 GB barrier!|url=http://www.msfn.org/board/topic/78592-enable48bitlba-break-the-137gb-barrier/|author=LLXX|version=1.1|date=2006-07-12|access-date=2013-09-03|archive-date=2013-12-12|archive-url=https://web.archive.org/web/20131212235154/http://www.msfn.org/board/topic/78592-enable48bitlba-break-the-137gb-barrier/|url-status=dead}}</ref> have modified the Windows 98 disk drivers to add unofficial support for 48-bit LBA to [[Windows 95 OSR2]], [[Windows 98]], [[Windows 98 SE]] and [[Windows ME]].

Some 16-bit and 32-bit operating systems supporting LBA48 may still not support disks larger than 2 [[TiB]] due to using 32-bit arithmetic only; a limitation also applying to many [[boot sector]]s.