Hardware Reference
In-Depth Information
ation for Windows (SIW) utility from
http://gtopala.com/
,
which tells you the BIOS date
fromyoursystemandspecificallywhetheryoursystemsupportstheEnhancedDiskDrive
specification (which means drives over 8.4GB).
If your BIOS does not support EDD (drives over 8.4GB), the three possible solutions are
as follows:
• Upgrade your motherboard BIOS to a 1998 or newer version that supports >8.4GB.
• Install a BIOS upgrade card, such as the UltraATA cards from
www.siig.com
.
• Install a software patch to add >8.4GB support.
Of these, the first one is the most desirable because it is usually free. Visit your mother-
board manufacturer's website to see whether it has newer BIOSs available for your
motherboardthatsupportlargedrives.Ifitdoesn't,thenextbestthingistouseacardsuch
as one of the UltraATA cards from SIIG (
www.siig.com
). I almost never recommend the
software-only solution because it merely installs a software patch in the boot sector area
of the hard drive, which can result in numerous problems when booting from different
drives, installing new drives, or recovering data.
Themostrecent2.2TBbarrierisnotatrueBIOSbarrierinthesamewaythattheprevious
barriers were. The issue here is not that the BIOS can't recognize drives 2.2TB or larger,
theproblemisthatitcan'tnormally
boot
fromthem.Tobootfroma2.2TBorlargerdrive
requiresaUEFI(UnifiedExtensibleFirmwareInterface)BIOS,orataminimumonewith
an enabled UEFI Boot option. Drives larger than 2.2TB can be used as data drives even
without a UEFI BIOS. Finally, note that both booting from and recognizing a 2.2TB or
larger drive as a data drive also requires that the drive be formatted using a GPT (GUID
Partition Table), and the operating system must have GPT support as well.
CHS Versus LBA
There are two primary methods to address (or number) sectors on an ATA drive. The first
method is called
CHS
(cylinder head sector) after the three respective coordinate numbers
used to address each sector of the drive. The second method is called
LBA
(logical block
address) and uses a single number to address each sector on a drive. CHS was derived
fromthephysicalwaydriveswereconstructed(andishowtheyworkinternally),whereas
LBA evolved as a simpler and more logical way to number the sectors regardless of the
internal physical construction.
Formoreinformationoncylinders,heads,andsectorsastheyareusedinternallywith-
in the drive,
see
“
HDD Operation
,
”
p.
450
(
Chapter 9
,
“
Hard Disk Storage
”).
The process of reading a drive sequentially in CHS mode starts with cylinder 0, head 0,
and sector 1 (which is the first sector on the disk). Next, all the remaining sectors on that
