distribute systems with an EFI system partition on the hard drive, which would add additional functions to the standard UEFI firmware stored on the motherboard's ROM. UEFI Capsule UEFI Capsule defines a Firmware-to-OS firmware update interface, marketed as modern and secure. Windows 8, Windows 8.1, Windows 10, and Fwupd for Linux each support the UEFI Capsule. Hardware Like BIOS, UEFI initializes and tests system hardware components (e.g. Memory training, PCIe link training, USB link training), and then loads the boot loader from a mass storage device or through a network connection. In x86 systems, the UEFI firmware is usually stored in the NOR flash chip of the motherboard. Classes UEFI machines can have one of the following classes, which were used to help ease the transition to UEFI: Class 0: Legacy BIOS Class 1: UEFI with a CSM interface and no external UEFI interface. The only UEFI interfaces are internal to the firmware. Class 2: UEFI with CSM and external UEFI interfaces Class 3: UEFI without a CSM interface and with an external UEFI interface Class 3+: UEFI class 3 that has Secure Boot enabled Starting from the 10th Gen Intel Core, Intel no longer provides Legacy Video BIOS for the iGPU (Intel Graphics Technology). Legacy boot with those CPUs requires a Legacy Video BIOS, which can still be provided by a video card. Boot stages SEC – Security Phase This is the first stage of the UEFI boot but may have platform specific binary code that precedes it. (e.g., Intel ME, AMD PSP, CPU microcode). It consists of minimal code written in assembly language for the specific architecture. It initializes a temporary memory (often CPU cache as RAM) and serves as the system's software root of trust with the option of verifying PEI before hand-off. PEI – Pre-EFI Initialization The second stage of UEFI boot consists of a dependency-aware dispatcher that loads and runs PEI modules (PEIMs) to handle early hardware initialization tasks such as main memory initialization and firmware recovery operations. Additionally, it is responsible for discovery of the current boot mode and handling many ACPI S0ix/ACPI S3 operations. In the case of ACPI S0ix/ACPI S3 resume, it is responsible for restoring many hardware registers to a pre-sleep state. PEI also uses CPU cache as RAM. DXE – Driver Execution Environment This stage consist of C modules and a dependency-aware dispatcher. With main memory now available, CPU, chipset,