Hardware Reference
In-Depth Information
age. Still, if you wanted to remove the HPA, there is a way to reset the max address, thus
exposing the HPA. Then you could run something like Partition Magic or Partition Com-
mandertoresizethemainpartitiontoincludetheextraspacethatwasformerlyhiddenand
unavailable. The only consequence is that you would lose access to the product recovery,
diagnostics, and backup applications preloaded by the OEM. For some people, this might
be desirable because future product recoveries could still be done via the recovery discs
(not usually shipped with the system anymore, but still available separately either for free
or for a minimal charge), and true hardware diagnostics can still be run via bootable flop-
pies or optical discs. Also, if you are replacing the hard disk, you can temporarily unhide
the HPA on the original drive, allowing it to be copied to a new drive. Alternatively, you
can use the OEM-supplied recovery discs to install the HPA on the new drive.
MostnewsystemsusingPhoenixBIOScomewiththeirrecoverysoftwareanddiagnostics
in the HPA because this is part of the newer Phoenix BIOS cores used by a large number
of OEMs on desktop and laptop systems built in 2003 or later.
Unified Extensible Firmware Interface (UEFI)
Unified Extensible Firmware Interface (UEFI) defines an interface between an OS and
computer hardware and firmware. The interface consists of tables containing system-spe-
cific information as well as boot and runtime services that are available to the OS loader
and to the OS after it is loaded. These tables and services provide an industry-standard
environment for running preboot applications, booting an OS, and providing drivers for
devicesthatneedtobeactiveduringboot.BecauseUEFIisbasedontheEFIspecification
originated by Intel, it is common to use the terms EFI and UEFI interchangeably.
UEFI was initially created by Intel as just EFI, and the EFI 1.01 specification was origin-
ally released in2000.EFI was anoutgrowth ofthe Intel Boot Initiative (IBI) program that
began in 1998. You can see the original Intel EFI specifications at
www.intel.com/tech-
nology/efi
.
Intel updated the EFI specification through 2003, and in 2005 it contributed
the specification to the Unified EFI (UEFI) Forum, a nonprofit organization formed to
promote and manage the UEFI standard. The UEFI Forum is led by representatives from
11 major companies including AMD, AMI, Apple, Dell, HP, IBM, Insyde, Intel, Lenovo,
Microsoft, and Phoenix Technologies. You can download the latest version of the UEFI
specification from the Unified EFI Forum at
www.uefi.org
.
UEFI and BIOS Limitations
The original PC BIOS was released in 1981 as part of the first IBM PC. The BIOS at that
timeconsistedofonly8KiBof16-bitcoderunninginwhatisknownasthe“realmode”of
Intel x86 (or compatible) processors, which limits memory addressability to just 1 mebib-
