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Target Disk Mode (sometimes referred to as TDM or Target Mode) is a boot mode unique to Macintosh computers. When a Mac that supports Target Disk Mode [1] is started with the 'T' key held down, its operating system does not boot. Instead, the Mac's firmware enables its drives to behave as a SCSI, FireWire, Thunderbolt, or USB-C external mass ...
An option ROM for the PC platform (i.e. the IBM PC and derived successor computer systems) is a piece of firmware that resides in ROM on an expansion card (or stored along with the main system BIOS), which gets executed to initialize the device and (optionally) add support for the device to the BIOS.
UEFI replaces the BIOS that was present in the boot ROM of all personal computers that are IBM PC compatible, [5] [6] although it can provide backwards compatibility with the BIOS using CSM booting. Unlike its predecessor, BIOS, which is a de facto standard originally created by IBM as proprietary software, UEFI is an open standard maintained ...
On Apple Mac computers using Intel x86-64 processor architecture, the EFI system partition is initially left blank and unused for booting into macOS. [13] [14]However, the EFI system partition is used as a staging area for firmware updates [15] and for the Microsoft Windows bootloader for Mac computers configured to boot into a Windows partition using Boot Camp.
Examples of first-stage (hardware initialization stage) boot loaders include BIOS, UEFI, coreboot, Libreboot and Das U-Boot. On the IBM PC, the boot loader in the Master Boot Record (MBR) and the Partition Boot Record (PBR) was coded to require at least 32 KB [51] [52] (later expanded to 64 KB [53]) of system memory and only use instructions ...
Early BIOS versions did not have passwords or boot-device selection options. The BIOS was hard-coded to boot from the first floppy drive, or, if that failed, the first hard disk. Access control in early AT-class machines was by a physical keylock switch (which was not hard to defeat if the computer case could be opened).
A modern PC with a bus rate of around 1 GHz and a 32-bit bus might be 2000x or even 5000x faster, but might have many more GB's of memory. With boot times more of a concern now than in the 1980s, the 30- to 60-second memory test adds undesirable delay for a benefit of confidence that is not perceived to be worth that cost by most users.
The original PXE client firmware extension was designed as an Option ROM for the IA-32 BIOS, so a personal computer (PC) was originally made PXE-capable by installing a network interface controller (NIC) that provided a PXE Option ROM. Today the client PXE code is directly included within the NIC's own firmware or as part of the UEFI firmware ...