DEC Alpha

Alpha

Designer	Digital Equipment Corporation
Bits	64-bit
Introduced	1992
Design	RISC
Type	Register-Register
Encoding	Fixed
Endianness	Bi
Extensions	Byte/Word Extension (BWX), Square-root and Floating-point Convert Extension (FIX), Count Extension (CIX), Motion Video Instructions (MVI)
Open	Yes
Registers
General purpose	31 plus always-zero R31
Floating point	31 plus always-0.0 F31

DEC Alpha registers

63 . . . 47 . . . 31 . . . 15 . . . 01 00 (bit position) General-purpose registers R0 R0 R1 R1 R2 R2 •   •   •   R29 R29 R30 R30            R31 (zero) R31, always zero Floating-point registers F0 F0 F1 F1 F2 F2 •   •   •   F29 F29 F30 F30            F31 (zero) F31, always zero Program counter          PC 0 0 Program Counter Control registers LR0 Lock Register 0 LR1 Lock Register 1 FPCR FP Control Register

Alpha, originally known as Alpha AXP, is a 64-bit reduced instruction set computing (RISC) instruction set developed by Digital Equipment Corporation (DEC), designed to replace their 32-bit VAX complex instruction set computer (CISC) instruction set. 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. Several third-party vendors also produced Alpha systems, including PC form factor motherboards.

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.

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