Hardware Reference
In-Depth Information
Running out of space causes numerous problems in a modern system, mainly because
Windows, as well as many newer applications, uses a large amount of drive space for
temporary files and virtual memory. When Windows runs out of room, system instability,
crashes, and data loss are inevitable.
Capacity Limitations
How big a hard drive you can use depends on many factors, including the interface,
drivers, OS, and file system you choose.
When the ATA interface was created in 1986, it had a maximum capacity limitation of
137GB (65,536×16×255 sectors). BIOS issues further limited capacity to 8.4GB in sys-
temsproducedearlierthan1998,andaslowas528MBinsystemsearlierthan1994.Even
after the BIOS issues were resolved, however, the initial 137GB limit of ATA remained.
Fortunately,thiswasbrokenintheATA-6specificationdraftedin2001.ATA-6augmented
the addressing scheme used by ATA to allow drive capacity to grow to 144PB (petabytes,
or quadrillion bytes), which is 248 sectors. This has opened the door allowing PATA and
SATA drives over 137GB to be released.
BIOS Limitations
Manyolder(pre-1998)BIOSscan'thandledrivesabovethe8.4GBlimit,andotherBIOSs
(pre-2002) have other limits, such as 137GB. Some drives ship with a setup or installa-
tiondisccontainingasoftwareBIOSsubstitute,suchasOntrack'sDiskManager,Phoenix
Technologies' EZ-Drive (Phoenix purchased EZ-Drive creator StorageSoft in January
2002), and their OEM offshoots (Drive Guide, MAXBlast, Data Lifeguard, and others).
However, I don't recommend using these because they can cause problems if you need
to boot from floppy or CD media or if you need to repair the nonstandard MBR these
products use.
Internal ATA drives larger than 137GB require 48-bit LBA support. This support
must
be
provided in the OS; it can also be provided in the BIOS, or both. It is best if both the OS
and the BIOS support it, but it can be made to work if only the OS has the support.
One of the following is required for 48-bit LBA support in the OS:
• Windows 7/Vista.
• Windows XP with Service Pack 1 (SP1) or later.
• Windows 2000 with Service Pack 4 (SP4) or later.
•Windows98/98SE/MeorNT4.0withtheIntelApplicationAccelerator(IAA)loaded.
This solution works only if your motherboard has an IAA-supported chipset. See
ht-
tp://downloadcenter.intel.com
and search for IAA for more information.
