The Unified Extensible Firmware Interface (UEFI) is meant to be an OS-Firmware interface, much like a standard BIOS is. This interface manages the PC boot and runtime services. It has been developed from the ground up, and thus should not be considered as an evolution to current existing BIOSes, which did not end up evolving much with current hardware. There were many limitations that led to its development; most importantly, the 16-bit processor mode and the maximum 1MB of addressable space deeply rooted into traditional BIOSes. This is because the original BIOS was designed off of the IBM 5150, equipped with an Intel 8088 processor. Heck, this 16-bit chip is now over 30 years old!
More recently, hard drive manufacturers have exceeded the 2.2TB size limitation of the Master Boot Record (MBR) partition scheme of our blue friends, so this also needed a replacement.
It all began in 1998 when Intel created the Boot Initiative (IBI) program, which eventually led to the release of the Extensible Firmware Interface (EFI) version 1.10. Later in 2005, the Unified EFI Forum was formed as a non-profit industry-wide organization with the goal of promoting adoption and continuing the development of the specification, starting from what Intel had already developed. This forum board of directors includes representatives of many big players in the industry, such as AMD, American Megatrends, Apple, IBM, Intel, Microsoft, and more. There is no cost associated for hardware vendors to implement the UEFI specification in their products. Today, UEFI is now at version 2.3.1, approved in April 2011. So, to solve the addressable memory and processor mode limitations, the UEFI is made to support 32-bit and 64-bit mode. In 64-bit, it can access the entire memory of the computer. Additionally, as of version 2.3, there exists bindings for all of these architectures: ARM, Itanium, x86 and x86-64. As for the hard drive capacity limitation, the MBR was replaced with a Globally Unique Identifier Partition Table (GPT), allowing for capacities up to 8ZiB (Zebibyte that is). Considering such a unit is 1 billion times bigger than a Terrabyte, how long will it be before the new limit is reached? If the capacity is multiplied by a factor of 10 every 5 years, roughly, it should take approximately half a century. It's difficult to predict where computers will be in 2060, however. Maybe Moore's Law will come to an end at some point? Maybe the quantum computers will take over? Another major difference with traditional BIOSes is the support for graphical menus and features. No user interface is defined in the UEFI specifications however, so it is up to the hardware vendor to implement one of their own. ASUS is one of the manufacturers to have done so. The result is called the "EZ Mode" of the UEFI BIOS. One important thing to note here is that it is still being referred to as a BIOS, which it is clearly not, but for the the average consumer it is going to cause much less confusion. So from now on, it's going to simply be called an UEFI. In the next page, Neoseeker is going to take a look at ASUS' particular implementation.
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