Apple–Intel architecture
The Apple–Intel architecture, or Mactel, is an unofficial name used for Apple Macintosh personal computers developed and manufactured by Apple Inc. that use Intel x86 processors, rather than the PowerPC and Motorola 68000 ("68k") series processors used in their predecessors or the ARM processors used in their successors. With the change in architecture, a change in firmware became necessary; Apple selected the Intel-designed Extensible Firmware Interface (EFI) as its comparable component to the Open Firmware used on its PowerPC architectures, and as the firmware-based replacement for the PC BIOS from Intel. With the change  in processor architecture to x86, Macs gained the ability to boot into x86-native operating systems (such as Microsoft Windows), while Intel VT-x brought near-native virtualization with macOS as the host OS. Technologies. Background. Apple uses a subset of the standard PC architecture, which provides support for Mac OS X and support for other operating systems. Hardware and firmware components that must be supported to run an operating system on Apple-Intel hardware include the Extensible Firmware Interface. The EFI and GUID Partition Table. With the change in architecture, a change in firmware became necessary. Extensible Firmware Interface  (EFI) is the firmware-based replacement for the PC BIOS from Intel. Designed by Intel, it was chosen by Apple to replace Open Firmware, used on PowerPC architectures. Since many operating systems, such as Windows XP and many versions of Windows Vista, are incompatible with EFI, Apple released a firmware upgrade with a Compatibility Support Module that provides a subset of traditional BIOS support with its Boot Camp product. GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical hard disk. It is a part of the Extensible Firmware Interface (EFI) standard proposed  by Intel as a substitute for the earlier PC BIOS. The GPT replaces the Master Boot Record (MBR) used with BIOS. Booting. To Mac operating systems. Intel Macs can boot in two ways: directly via EFI, or in a "legacy" BIOS compatibility mode. For multibooting, holding down "Option" gives a choice of bootable devices, while the rEFInd bootloader is commonly used for added configurability. Legacy Live USBs cannot be used on Intel Macs; the EFI firmware can recognize and boot from USB drives, but it can only do this in EFI mode–when the firmware switches to BIOS mode , it no longer recognizes USB drives, due to lack of a BIOS-mode USB driver. Many operating systems, such as earlier versions of Windows and Linux, could only be booted in BIOS mode, or were more easily booted or perform better when booted in BIOS mode, and thus USB booting on Intel-based Macs was for a time largely limited to Mac OS X, which can easily be booted via EFI. To non-Mac operating systems. On April 5, 2006, Apple made available for download a public beta version of Boot Camp, a collection of technologies that allows users of  Intel-based Macs to boot Windows XP Service Pack 2. The first non-beta version of Boot Camp is included in Mac OS X v10.5, "Leopard." Before the introduction of Boot Camp, which provides most hardware drivers for Windows XP, drivers for XP were difficult to find. Linux can also be booted with Boot Camp. Differences from standard PCs. Intel-based Mac computers use very similar hardware to PCs from other manufacturers that ship with Microsoft Windows or Linux operating systems. In particular, CPUs, chipsets, and GPUs are entirely compatible. However, Apple computers also include some custom hardware and design  choices not found in competing systems: Some of these differences can pose as obstacles both to running macOS on non-Apple hardware and booting alternative operating systems on Mac computers – Apple only provides drivers for its custom hardware for macOS and Microsoft Windows (as part of Boot Camp); drivers for other operating systems such as Linux need to be written by third parties, usually volunteer free software enthusiasts. Digital Rights Management. Digital Rights Management in the Apple–Intel architecture is accomplished via the "Dont Steal Mac OS X.kext," sometimes referred to as DSMOS or DSMOSX, a file present in  Intel-capable versions of the Mac OS X operating system. Its presence enforces a form of Digital Rights Management, preventing Mac OS X being installed on stock PCs. The name of the kext is a reference to the Mac OS X license conditions, which allow installation on Apple hardware only. According to Apple, anything else is stealing Mac OS X. The kext is located at /System/Library/Extensions on the volume containing the operating system. The extension contains a kernel function called that performs AES decryption of "apple-protected" programs. A system lacking a proper key will not be able  to run the Apple-restricted binaries, which include , , , , , , , , , or . After the initial announcement of first Intel-based Mac hardware configurations, reporting a Trusted Platform Module among system components, it was believed that the TPM is responsible for handling the DRM protection. It was later proven to not be the case. The keys are actually contained within the System Management Controller, a component exclusive to Apple computers, and can be easily retrieved from it. These two 32-byte keys form a human-readable ASCII string copyrighted by Apple, establishing another possible line of legal defence against prospective clone makers. Virtualization. The  Intel Core Duo (and later, including the current i5, i7, i9, and Xeon) processors found in Intel Macs support Intel VT-x, which allows for high performance (near-native) virtualization that gives the user the ability to run and switch between two or more operating systems simultaneously, rather than having to dual-boot and run only one operating system at a time. The first software to take advantage of this technology was Parallels Desktop for Mac, released in June 2006. The Parallels virtualization products allow users to use installations of Windows XP and later in a virtualized mode while running  OS X. VirtualBox is virtualization software from Oracle Corporation, which was released January 2007. Available for Mac OS X as well as other host operating systems, it supports Intel VT-x and can run multiple other guest operating systems, including Windows XP and later. It is available free of charge under either a proprietary license or the GPL free software license and is used by default when running Docker images of other operating systems VMware offers a product similar to Parallels called Fusion, released August 2007. VMware's virtualization product also allows users to use installations of Windows XP and  later under OS X. Regardless of the product used, there are inherent limitations and performance penalties in using a virtualized guest OS versus the native macOS or booting an alternative OS solution offered via Boot Camp.