DEC Alpha

AlphaAlpha AXPAlpha processor32 to 200Alpha computersAlpha CPUAlpha/AXPDEC/Compaq AlphaDigital Equipment Corporation's Alpha processorDigital's Alpha platform
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) ISA.wikipedia
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Reduced instruction set computer

RISCreduced instruction set computingreduced instruction set
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) ISA.
The many varieties of RISC designs include ARC, Alpha, Am29000, ARM, Atmel AVR, Blackfin, i860, i960, M88000, MIPS, PA-RISC, Power ISA (including PowerPC), RISC-V, SuperH, and SPARC.

VAX

DEC VAXVAX 11/780DEC VAX ULTRIX
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) ISA.
VAX was succeeded by the DEC Alpha instruction set architecture.

OpenVMS

VMSVAX/VMSDECwindows
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
OpenVMS also runs on DEC Alpha systems and the HP Itanium-based families of computers.

Digital Equipment Corporation

DECDigitalDigital Equipment
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) ISA.
DEC's last major attempt to find a space in the rapidly changing market was the DEC Alpha 64-bit RISC instruction set architecture.

Tru64 UNIX

Tru64Digital UNIXOSF/1
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
Tru64 UNIX is a discontinued 64-bit UNIX operating system for the Alpha instruction set architecture (ISA), currently owned by Hewlett-Packard (HP).

Windows 2000

2000Windows 2000 ServerMicrosoft Windows 2000
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
During development, there was a build for the Alpha which was abandoned some time after RC1 after Compaq announced they had dropped support for Windows NT on Alpha.

Windows NT

NTMicrosoft Windows NTWindows NT family
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
Initially, it supported several instruction set architectures, including IA-32, MIPS, and DEC Alpha; support for PowerPC, Itanium, x64, and ARM were added later.

Windows NT 4.0

NT 4.0Windows NT 4NT 4
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
Windows NT 4.0 is the last major release of Microsoft Windows to support the Alpha, MIPS or PowerPC CPU architectures as Windows 2000 dropped support for those architectures.

NetBSD

BSDCryptographic Device DriverNetBSD Foundation
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
This permits a particular device driver for a PCI card to work without modifications, whether it is in a PCI slot on an IA-32, Alpha, PowerPC, SPARC, or other architecture with a PCI bus.

Itanium

Itanium 2IA-64Intel Itanium
Compaq, already an Intel customer, phased out Alpha in favor of the forthcoming Hewlett-Packard/Intel Itanium architecture, and sold all Alpha intellectual property to Intel in 2001, effectively killing the product. On June 25, 2001, Compaq announced that Alpha would be phased out by 2004 in favor of Intel's Itanium, canceled the planned EV8 chip, and sold all Alpha intellectual property to Intel.
Compaq and Silicon Graphics decided to abandon further development of the Alpha and MIPS architectures respectively in favor of migrating to IA-64.

Alpha 21064

DECchip 2106421064Alpha 21066
The first version, the Alpha 21064 (otherwise known as the EV4) was introduced in November 1992 running at up to 192 MHz; a slight shrink of the die (the EV4S, shrunk from 0.75 µm to 0.675 µm) ran at 200 MHz a few months later.
The Alpha 21064 is a microprocessor developed and fabricated by Digital Equipment Corporation that implemented the Alpha (introduced as the Alpha AXP) instruction set architecture (ISA).

Red Hat Linux

Red HatRHLBiltmore
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
The decision to ship an unstable GCC version was due to GCC 2.95's bad performance on non-i386 platforms, especially DEC Alpha.

PALcode

The PRISM's Epicode was developed into the Alpha's PALcode, providing an abstracted interface to platform- and processor implementation-specific features.
In computing, in the Alpha instruction set architecture, PALcode (Privileged Architecture Library code) is the name used by DEC for a set of functions in the SRM or AlphaBIOS firmware, providing a hardware abstraction layer for system software, covering features such as cache management, translation lookaside buffer (TLB) miss handling, interrupt handling and exception handling.

64-bit computing

64-bit64 bit64
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) ISA.
64-bit CPUs have been used in supercomputers since the 1970s (Cray-1, 1975) and in reduced instruction set computing (RISC) based workstations and servers since the early 1990s, notably the MIPS R4000, R8000, and R10000, the DEC Alpha, the Sun UltraSPARC, and the IBM RS64 and POWER3 and later POWER microprocessors.

Gentoo Linux

GentooHardened GentooFuntoo
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.
It is officially supported and considered stable on IA-32, x86-64, IA-64, PA-RISC, 32-bit and 64-bit PowerPC, 64-bit SPARC, DEC Alpha, and both 32- and 64-bit ARM architectures.

Alpha 21464

21464EV8EV8 (Alpha 21464)
On June 25, 2001, Compaq announced that Alpha would be phased out by 2004 in favor of Intel's Itanium, canceled the planned EV8 chip, and sold all Alpha intellectual property to Intel.
The Alpha 21464 is an unfinished microprocessor that implements the Alpha instruction set architecture (ISA) developed by Digital Equipment Corporation and later by Compaq after it acquired Digital.

Instruction set architecture

instruction setinstructionsinstruction
Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) ISA.
While embedded instruction sets such as Thumb suffer from extremely high register pressure because they have small register sets, general-purpose RISC ISAs like MIPS and Alpha enjoy low register pressure.

FreeBSD

TrustedBSDFreeBSD kernel*BSD
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.

Processor register

registersregistergeneral purpose register
The architecture defined a set of 32 integer registers and a set of 32 floating-point registers in addition to a program counter, two lock registers and a floating-point control register (FPCR).
In Alpha this is also done for the floating-point register file.

Debian

Debian GNU/LinuxDebian LinuxDebian Project
Operating systems that supported Alpha included OpenVMS (previously known as OpenVMS AXP), Tru64 UNIX (previously known as DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after NT 4.0; and pre-release Windows 2000 RC1), Linux (Debian, SUSE, Gentoo and Red Hat), BSD UNIX (NetBSD, OpenBSD and FreeBSD up to 6.x), Plan 9 from Bell Labs, as well as the L4Ka::Pistachio kernel.

Status register

Condition codecondition code registercondition codes
The Alpha does not have condition codes for integer instructions to remove a potential bottleneck at the condition status register.
Some CPU architectures, such as the MIPS and Alpha, do not use a dedicated flag register.

DEC Prism

Prism
Alpha was born out of an earlier RISC project named Prism (Parallel Reduced Instruction Set Machine), itself the product of several earlier projects.
The next year work on the Alpha started, based heavily on the Prism design.

Alpha 21164

21164Alpha 21164A21164A
These instructions were first introduced in the 21164A (EV56) microprocessor and are present in all subsequent implementations.
The Alpha 21164, also known by its code name, EV5, is a microprocessor developed and fabricated by Digital Equipment Corporation that implemented the Alpha instruction set architecture (ISA).

Microprocessor

microprocessorsprocessorprocessors
Alpha was implemented in microprocessors originally developed and fabricated by DEC. These microprocessors were most prominently used in a variety of DEC workstations and servers, which eventually formed the basis for almost all of their mid-to-upper-scale lineup.
Soon every major vendor was releasing a RISC design, including the AT&T CRISP, AMD 29000, Intel i860 and Intel i960, Motorola 88000, DEC Alpha.

Delay slot

branch delay slotdelay slotsdelayed branch logic
MIPS, PA-RISC, ETRAX CRIS, SuperH, and SPARC are RISC architectures that each have a single branch delay slot; PowerPC, ARM, Alpha, and RISC-V do not have any.