===== Glossary =====

Terms used throughout this wiki and in Alpha documentation. See also the [[:faq|FAQ]].

==== Processors ====

Digital named each Alpha processor design with an EV number, usually expanded as "Extended VAX", and sold it under a 21//x//64 part number. The consoles report part numbers, so the EV name often has to be looked up; see [[hardware:cpus#names_and_type_codes|CPUs: Names and type codes]].

^ Name ^ Part ^ Notes ^
| **EV4** | 21064 | The first Alpha, 1992. Supported by Linux up to 6.9 |
| **EV45** | 21064A | EV4 with larger caches and a faster FPU. Up to Linux 6.9 |
| **LCA4**, **LCA45** | 21066, 21068, 21066A, 21068A | "Low Cost Alpha": an EV4 core with an integrated memory and PCI controller. Up to Linux 6.9 |
| **EV5** | 21164 | Four-issue, with an on-chip secondary cache. Up to Linux 6.9 |
| **EV56** | 21164A | EV5 with the BWX extension. The oldest processor current kernels support |
| **PCA56**, **PCA57** | 21164PC | A cheaper EV56 without the on-chip secondary cache, and with MVI |
| **EV6** | 21264 | Out-of-order execution. Adds FIX, and has BWX and MVI |
| **EV67** | 21264A | Adds CIX |
| **EV68** | 21264B, 21264C, 21264D | Die shrinks of the EV67, in several variants (EV68AL, EV68CB, EV68CX) |
| **EV7** | 21364 | EV68 core with integrated memory controllers and interprocessor links, used in the ES47, ES80, and GS1280 |
| **EV79** | 21364A | A die shrink of the EV7, canceled |
| **EV8** | 21464 | A four-thread simultaneous multithreading design, canceled in 2001 |

==== Instruction set extensions ====

The Alpha architecture was extended after the first processors shipped. Each extension has a bit in the result of the [[documentation:amask|amask]] instruction, and a GCC ''-m'' option. See [[documentation:instruction_set#isa_extensions|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 [[documentation:porting:byte_word_access|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.

==== Programming ====

  * **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 [[documentation:toolchains#relocation_truncated_to_fit|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 [[documentation:porting:floating_point|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 [[documentation:porting:floating_point#trap_modes_and_software_completion|Floating Point: Trap modes and software completion]].
  * **LRA**, the Local Register Allocator, GCC's replacement for its older reload pass. [(>[[https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/lra.cc|gcc/lra.cc]], GCC)] GCC's Alpha back end still uses reload and has to move to LRA; see [[:status#core_projects|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 [[documentation:porting:unaligned_access|Unaligned Access]].

==== Firmware and booting ====

  * **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 [[software:firmware:srm#palcode|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 [[software:firmware:srm|SRM Console]] and [[documentation:srm|Using the SRM Console]].
  * **ARC**, the menu-driven firmware for Windows NT, after the Advanced RISC Computing specification. See [[software:firmware:arc|ARC Firmware]].
  * **AlphaBIOS**, the later, PC BIOS-like firmware for Windows NT that replaced ARC. Also on the [[software:firmware:arc|ARC Firmware]] page.
  * **ARCSBIOS**, the firmware of Deskstation's Ruffian board. See [[software:firmware:arc#arcsbios|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 [[software:boot_loaders:milo|MILO]].
  * **aboot**, the Linux boot loader for SRM systems. See [[software:boot_loaders:aboot|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 [[software:firmware:srm#hwrpb|SRM Console: HWRPB]].
  * **LFU**, the Loadable Firmware Update utility, which installs firmware from the Alpha Systems Firmware Update CD. See [[software:firmware:srm#updating_firmware|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 [[documentation:srm#remote_management|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. [(>{{wiki:software:firmware:alphaserver_es47_es80_gs1280_srm_console_reference.pdf?linkonly|AlphaServer ES47/ES80/GS1280 SRM Console Reference}}, p. 7)] They do not always correspond to Linux names. See [[software:firmware:srm#device_names|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. [(>{{wiki:documentation:references:alpha_architecture_reference_manual_4th_edition.pdf?linkonly|Alpha Architecture Reference Manual, Fourth Edition}}, section 14.1.1, p. 14-2)] Linux logs them, and SRM may report them after Linux halts. See [[documentation:kernel#debugging|Kernel: Debugging]].
  * **BSD disklabel**, the partition table format that SRM systems boot from. See [[documentation:installation#partitioning|Installation]].

==== Systems and chipsets ====

  * **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 [[hardware:chipsets|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 [[hardware:systems#naming|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. [(>[[https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/alpha/Kconfig?h=v7.3-rc1|arch/alpha/Kconfig]], Linux 7.3)] Distribution kernels are generic. See [[documentation:kernel#configuring_for_a_system|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 [[documentation:kernel#configuring_for_a_system|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 [[documentation:porting:byte_word_access|Byte and Word Access]].

==== Names ====

  * **AXP**, Digital's original marketing name for Alpha, as in "DEC OSF/1 AXP" and "OpenVMS AXP". It was dropped in the mid-1990s. [(>[[https://github.com/alphalinux/mailing-list-archives/blob/main/comp-os-linux-announce-mbox/googlegroups-1994-November.mbox#L36280|"Linux/Alpha Progress Report - Part 2"]], Jim Paradis, comp.os.linux.announce, 18 Nov 1994)]
  * **Digital**, **DEC**, **Compaq**, **HP**: Digital Equipment Corporation designed Alpha, and was bought by Compaq in 1998, which merged with HP in 2002. See [[history:companies|Companies]].
  * **API**, Alpha Processor, Inc., later API NetWorks, the Samsung-backed company that sold Alpha motherboards such as the UP1000 and UP2000. See [[history:companies|Companies]].
  * **OSF/1**, **Digital UNIX**, **Tru64 UNIX**: successive names of Digital's UNIX for Alpha. See [[software:operating_systems:tru64|Tru64 UNIX]].

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