Terms used throughout this wiki and in Alpha documentation. See also the FAQ.

Digital named each Alpha processor design with an EV number, usually expanded as "Extended VAX", and sold it under a 21x64 part number. The consoles report part numbers, so the EV name often has to be looked up; see CPUs: Names and type codes.

The Alpha architecture was extended after the first processors shipped. Each extension has a bit in the result of the amask instruction, and a GCC -m option. See Instruction Set: ISA extensions.

• BWX, the byte/word extension: loads and stores of single bytes and 16-bit words, and sign extension. First in the EV56. Without it, a byte store is a read-modify-write sequence of several instructions, which cannot be made atomic; this is why Linux 6.10 dropped pre-EV56 processors. See Byte and Word Access.
• MVI, the motion video instructions: byte and word minimum and maximum, pixel error, and pack and unpack. First in the PCA56.
• FIX, the floating-point extension: square root, and moves between the integer and floating-point registers. First in the EV6.
• CIX, the count extension: count leading zeros, trailing zeros, and population. First in the EV67.

• gp, the global pointer: register $29, through which Alpha code reaches global data and the addresses of other functions, using 16-bit displacements. The limited reach is the cause of "relocation truncated to fit" errors; see Toolchains.
• -mieee, the GCC option that makes floating-point code handle NaNs, infinities, and denormals as IEEE 754 requires, by marking instructions for software completion. Without it, such values raise SIGFPE. See Floating Point.
• Software completion, the kernel's finishing of a floating-point operation that the hardware traps on, such as one with a denormal operand, so that it returns the IEEE result. It applies only to instructions compiled for it, with -mieee. See Floating Point: Trap modes and software completion.
• LRA, the Local Register Allocator, GCC's replacement for its older reload pass. ¹⁾ GCC's Alpha back end still uses reload and has to move to LRA; see Current Status: Core projects.
• Unaligned trap, the exception taken when a load or store is not aligned to its size. Linux completes the access in software and logs an "unaligned trap" message. See Unaligned Access.

• PALcode, the Privileged Architecture Library: a layer of code that runs in a special processor mode, between the hardware and the operating system, and implements operations such as memory management, interrupts, and system calls. Each operating system family has its own; Linux uses the OSF/1 (Tru64 UNIX) PALcode. Firmware supplies the PALcode, which is why ARC systems cannot run Linux without MILO. See SRM Console: PALcode.
• SRM, the console firmware for OpenVMS and Digital UNIX, named after the Alpha System Reference Manual that specifies it. It has a >>> command prompt, and is the firmware Linux should boot from. See SRM Console and Using the SRM Console.
• ARC, the menu-driven firmware for Windows NT, after the Advanced RISC Computing specification. See ARC Firmware.
• AlphaBIOS, the later, PC BIOS-like firmware for Windows NT that replaced ARC. Also on the ARC Firmware page.
• ARCSBIOS, the firmware of Deskstation's Ruffian board. See ARC Firmware: ARCSBIOS.
• MILO, the Alpha Linux Miniloader: a boot loader that brings its own PALcode, so that Linux can boot from ARC and AlphaBIOS. See MILO.
• aboot, the Linux boot loader for SRM systems. See aboot.
• HWRPB, the Hardware Restart Parameter Block: the structure in which the firmware describes the system to the operating system, including its type, processors, and memory. See SRM Console: HWRPB.
• LFU, the Loadable Firmware Update utility, which installs firmware from the Alpha Systems Firmware Update CD. See Updating firmware.
• RMC, the remote management console of the later Compaq servers: a separate controller, reached through COM1, that can power, halt, and reset the system. See Using the SRM Console.
• SRM device names, the names the SRM console gives devices, such as dka0 or dqa0. The first two letters give the driver, for example dk for a SCSI drive, dq for an IDE drive, pk for a SCSI controller, and ew for an Ethernet port; the third letter the adapter; and the number the unit, 100 times the SCSI ID for SCSI devices. ²⁾ They do not always correspond to Linux names. See SRM Console: Device names.
• Machine check, the exception by which the processor reports a hardware error condition, as opposed to an exception caused by an instruction or an interrupt from a device. Machine checks cannot be disabled. ³⁾ Linux logs them, and SRM may report them after Linux halts. See Kernel: Debugging.
• BSD disklabel, the partition table format that SRM systems boot from. See Installation.

• Core logic, Digital's term for the chipset that connects the processor to memory and the I/O buses. Its name usually names the kernel platform, such as CIA, Pyxis, Tsunami, or Titan. See Chipsets.
• Codename, the internal name of a system, such as Miata for the Personal Workstation or Clipper for the ES40. The kernel uses codenames for its platforms. See Systems: Naming.
• Generic kernel, a kernel built with CONFIG_ALPHA_GENERIC, which runs on all supported Alpha systems by choosing the machine vector at boot. ⁴⁾ Distribution kernels are generic. See Kernel: Configuring for a system.
• Machine vector, the kernel's table of platform-specific routines. A generic kernel picks one at boot from the HWRPB, and the alpha_mv= option overrides the choice. See Kernel.
• Hose, a PCI bus root, on systems with more than one. SRM device names and the kernel both number them.
• Sparse and dense space, the two ways Alpha systems map PCI memory and I/O space. Sparse space encodes the access size in the address, so that pre-BWX processors can make byte and word accesses to devices; dense space maps device memory directly. See Byte and Word Access.

• AXP, Digital's original marketing name for Alpha, as in "DEC OSF/1 AXP" and "OpenVMS AXP". It was dropped in the mid-1990s. ⁵⁾
• Digital, DEC, Compaq, HP: Digital Equipment Corporation designed Alpha, and was bought by Compaq in 1998, which merged with HP in 2002. See Companies.
• API, Alpha Processor, Inc., later API NetWorks, the Samsung-backed company that sold Alpha motherboards such as the UP1000 and UP2000. See Companies.
• OSF/1, Digital UNIX, Tru64 UNIX: successive names of Digital's UNIX for Alpha. See Tru64 UNIX.