It is possible to have support for both 32-bit and 64-bit UEFI in one BIOS, but it requires additional work and ROM space, so this may not be commonly implemented. A 32-bit UEFI firmware core must be used to install a 32-bit OS and likewise 64-bit UEFI for a 64-bit OS. However, there is a limitation on installing Windows on devices with UEFI firmware. Most of UEFI-based computers come with 64-bit UEFI but there are also some Windows 8 tablets that use 32-bit UEFI, such as Dell Venue 8/11 Pro, Toshiba Encore, Acer Iconia W3/W4, Lenovo MIIX 2, Lenovo ThinkPad Tablet 2 and ASUS Transformer Book T100/T300. Many new computers are shipping with UEFI firmware instead of standard BIOS.
UEFI (Unified Extensible Firmware Interface) is a standard firmware interface for PCs, designed to replace legacy BIOS (basic input/output system).
