Administrator Guide

5 : BIOS vs. UEFI | Doc ID 20444677 | June 2018
1 Introduction
Traditionally, the system BIOS performs initialization, boot, system management, and configuration tasks. The
BIOS initializes the system’s processors, memory, bus controllers, and I/O devices. After initialization is
complete, the BIOS passes control to operating system (OS) software. The OS loader uses basic services
provided by the system BIOS to locate and load OS modules into system memory. After booting the system,
the BIOS and embedded management controllers execute system management algorithms, which monitor
and optimize the condition of the underlying hardware. BIOS configuration settings enable fine-tuning of the
performance, power management, and reliability features of the system.
The Unified Extensible Firmware Interface (UEFI) does not change the traditional purposes of the system
BIOS. To a large extent, a UEFI-compliant BIOS performs the same initialization, boot, configuration, and
management tasks as a traditional BIOS. However, UEFI does change the interfaces and data structures the
BIOS uses to interact with I/O device firmware and operating system software. The primary intent of UEFI is
to eliminate shortcomings in the traditional BIOS environment, enabling system firmware to continue scaling
with industry trends.
Since 2010, Dell EMC has offered servers that support both the traditional BIOS boot mode and UEFI boot
mode. However, the system administrator must choose the boot mode before deploying the server to its
operating environment. This paper helps system administrators understand the implications of each boot
mode. First, the paper explains the limitations of the traditional BIOS that UEFI resolves. Next, it describes
functionality that is available in UEFI boot mode that is not available in BIOS boot mode. Finally, the paper
provides considerations for deploying a server in UEFI boot mode in the midst of a traditional datacenter
infrastructure.