Firmware is software embedded into hardware. Hardware like GPUs, hard drives, SSDs (solid state drives)and more can also come with firmware.
Also commonly referred to as the BIOS, motherboard firmware defines how a PC turns on, which drive it boots from, what peripherals it recognizes and even the frequency at which it runs the CPU.
There are two different types of BIOS:
- UEFI (Unified Extensible Firmware Interface) BIOS - Any modern PC has a UEFI BIOS. UEFI can handle drives that are 2.2TB or larger thanks to it ditching the Master Boot Record (MBR) method in favor of the more modern GUID Partition Table (GPT) technique. While Intel PCs are moving away from Legacy BIOS and toward UEFI firmware, Apple’s Mac PCs never used BIOS.
- Legacy BIOS (Basic Input/Output System) - Older motherboards have legacy BIOS firmware for turning on the PC. While, like UEFI, it controls how the CPU and components interact, Legacy BIOSes have some limitations. They can't recognize drives that are larger than 2.1TB and they have text-only menus in their setup programs.
This article is part of the Tom's Hardware Glossary.
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