Hardware Reference
In-Depth Information
And either of the following is required for 48-bit LBA support in the BIOS:
• A motherboard BIOS with 48-bit LBA support (usually dated September 2002 or
later)
• An adapter card with onboard BIOS that includes 48-bit LBA support
If you have both OS and BIOS support for 48-bit LBA, you can simply install and use
the drive like any other internal drive. On the other hand, if you do not have 48-bit LBA
support in the BIOS, but you do have it in the OS, portions of the drive past 137GB are
not recognized or accessible until the OS is loaded. This means that if you are installing
the OS to a blank hard drive and booting from an original XP (pre-SP1) CD or earlier,
you need to partition up to the first 137GB of the drive at installation time. After the OS
is fully installed andthe service packs added, the remainder ofthe drive beyond137GB is
recognized. At that point, you can then either partition the remainder of the drive beyond
137GB using the XP Disk Management tools or use a third-party partitioning program
such as PartedMatic (
www.PartedMagic.com
)
to resize the first partition to use the full
drive.
IfyouarebootingfromanXPSP1orlaterCD(meaningaCDwithServicePack1already
applied), you can recognize and access the entire drive during the OS installation and par-
tition the entire drive as a single partition greater than 137GB if you like.
Booting from 2.2TB or larger drives requires a newer type of BIOS called UEFI (Unified
Extensible Firmware Interface), which supports booting from a new type of partition
formatcalledGUID(globallyuniqueidentifier)PartitionTable(GPT).Thisisbecausethe
traditional MBR disk format only supports drives up to 2.199TB, and legacy (non-UEFI)
BIOS can only boot from MBR-formatted drives.
IfyouneedmoreorfasterPATAorSATAinterfaceconnections,youcanuseadd-oncards
from companies such as Promise Technology (
www.promise.com
)
. These cards support
drives up to and beyond the 137GB limit imposed by the ATA-5 and older standards.
Note that external USB and FireWire drives don't have these capacity issues because they
don't rely on the ROM BIOS for support and use OS-managed drivers instead.
SCSI was designed from the beginning with fewer limitations than ATA, which is why
SCSI is more commonly used in high-performance file servers, workstations, and other
high-performance computer systems. Even though SCSI originated prior to ATA, the ar-
chitects had the foresight to allow SCSI to address devices less than 2.2TB (terabytes, or
trillion bytes) in capacity (2
32
sectors). In 2001, the SCSI command set was further up-
gradedtosupportdrivesupto9.44ZB(zettabytes,orsextillionbytes)incapacity(2
64
sec-
tors).BecauseSCSIwasinitiallydesignedwithfewerlimitationsandgreaterperformance
