<storage> (LBA) A hard disk sector addressing scheme used
on all SCSI hard disks, and on ATA-2 conforming IDE hard
disks. The addressing conversion is performed by the hard
disk firmware.
Prior to LBA, combined limitations of IBM PC BIOS and
ATA restricted the useful capacity of IDE hard disks on IBM
PCs and compatibles to 1024 cylinders * 63 sectors per track *
16 heads * 512 bytes per sector = 528 million bytes = 504
megabytes. Modern BIOSes select LBA mode automatically, and
work around the 1024-cylinder BIOS limit by representing a
hard disk to the OS as having e.g. half as many cylinders and
twice as many heads. However, there is still an unbreakable
BIOS disk size limit of 1024 cylinders * 63 sectors per track
* 256 heads * 512 bytes per sector = 8 gigabytes, but modern
OSes (including Windows 9x, Windows NT and Linux) are
not affected by it, since they issue direct LBA-based calls,
bypassing the BIOS hard disk services completely.
(2000-04-30)
Nearby terms:
logic « logical « logical address « Logical Block Addressing » logical complement » Logical Interchange Format » Logical Link Control
