Question Of The Week
UEFI Vs BIOS
UEFI (Unified Extensible Firmware Interface) is an interface between hardware and the operating system. It is similar to BIOS (Basic Input/ Output System ) but is not specific to any processor architecture. BIOS is specific to the 16-bit x86 processor architecture.
BIOS boots by reading the first sector on a hard disk and executing it; this boot sector in turn locates and runs additional code (System OS). UEFI boots by loading .EFI program files from a partition on the hard disk, known as the EFI System Partition (ESP).
The BIOS system is very limiting because of space constraints and 16-bit code, whereas modern computers use 32-bit or 64-bit without space constraints. UEFI can be faster causing a reduction in the total boot time.
UEFI supports a feature called Secure Boot, as the name suggests, to improve security. Secure Boot requires a digital "signature" of boot loaders, which in turn should require signing of kernels, and so on up the chain. This should make it harder for malware authors to insert their code into the pre-boot process, thus improving security. This sounds good, but it also complicates dual-boot configurations.
UEFI provides a shell environment, which can be used to execute other UEFI applications. Commands available in the UEFI shell can be used to obtain information about the system, to modify boot manager, to load UEFI drivers, to run partitioning programs etc.,
In Windows, the boot disk's partition table type is linked to the firmware type (MBR to BIOS; GPT to UEFI). If it's GPT (GUID {Global Unique ID} Partition Table), you booted in EFI mode, and if it's MBR (Master Boot Record), you booted in BIOS mode. MBR tops out at 2TB (assuming standard sector sizes), which means that UEFI is a practical necessity to boot Windows for larger than 2TB disks.
The Compatibility Support Module (CSM) is a component of the UEFI firmware which provides legacy BIOS compatibility by emulating a BIOS environment, allowing the use of legacy operating systems (those do not support UEFI). CSM also features legacy System Management Mode functionality called CompatibilitySMM, providing USB legacy support for keyboard and mouse, by emulating their classic PS/2 counterparts.
UEFI requires the firmware and operating system loader (kernel) to be size-matched; for example, a 64-bit UEFI firmware can only load a 64-bit UEFI operating system boot loader. 32-bit UEFI is not prevalent since vendors did not have interest in producing native 32-bit UEFI firmware because of the mainstream status of 64-bit computing. Although Windows 8 includes 32-bit support, only the 64-bit versions of Microsoft Windows Vista and Windows 7 can be installed in UEFI firmware.
Now you know why you had problems in installing 32-bit Windows 7 in your latest laptop which either had DOS or Linux from the factory !! Try the legacy BIOS compatibility mode in the UEFI settings screen or simply go for Windows 8 (32-bit/64-bit).
