DEC Alpha | 1992

 Alpha (originally named Alpha AXP) is a 64-bit Reduced Instruction Set Computer (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). Alpha was designed to replace the 32-bit VAX Complex Instruction Set Computer (CISC) and aimed to be a high-performance RISC processor that could compete in the Unix workstation market.

Alpha was implemented in various microprocessors developed and manufactured by DEC, which were primarily used in DEC's workstations and servers. These systems constituted nearly all of DEC's mid-to-high-end product lineup. Several third-party vendors also built Alpha systems, including motherboards in PC form.

Operating systems supporting Alpha included OpenVMS (formerly OpenVMS AXP), Tru64 UNIX (formerly DEC OSF/1 AXP and Digital UNIX), Windows NT (discontinued after version 4.0, including versions prior to Windows 2000 RC2), Linux (Debian, SUSE, Gentoo, Red Hat), BSD UNIX (NetBSD, OpenBSD, FreeBSD 6.x), Bell Labs' Plan 9, and the L4Ka::Pistachio kernel. Although an Alpha port of Ultrix was in development during the early stages, it was never released as a product.

The Alpha architecture was sold to Compaq in 1998 along with DEC, and since Compaq was already an Intel x86 customer, it announced in 2001 that it would phase out Alpha and switch to Intel's Itanium architecture through its "Hollywood partnership." As a result, Intel acquired the intellectual property of Alpha, and Alpha products were eventually discontinued. After Compaq was acquired by HP in 2002, development of existing product lines continued, and Alpha-based systems were sold until 2004. The sale of Alpha products was officially discontinued in April 2007.

The Alpha architecture originated from DEC's earlier RISC project, PRISM, which was the result of several early projects. PRISM was a flexible system designed to support applications like Unix while converting only a small portion of DEC's existing VAX/VMS software for execution. The new operating system, MICA, was intended to support both ULTRIX and VAX/VMS interfaces on a common kernel, making it easier to port software from both platforms.

PRISM's design, which began in 1985, evolved as the computer market changed, resulting in delays. By the summer of 1987, it was shifted to a 64-bit design, which was quite early for microprocessor design. In October 1987, Sun Microsystems released the first workstation using the SPARC processor, the Sun-4, which ran Unix much faster than DEC's then-latest Sun-3 design. This change led to PRISM's design being revised back to 32-bits and targeted at the Unix market, which delayed development further.

As the release of PRISM was continually delayed, a team in DEC's Palo Alto office decided to develop their own workstation. They chose the MIPS R2000 processor and completed a workstation running Ultrix in just 90 days. This caused significant controversy within the company, leading to a management meeting in July 1988. While PRISM was faster than the R2000, the R2000 machine could be released to the market by January 1989, effectively nullifying PRISM's second role. As a result, PRISM was canceled.

After the meeting, Ken Olsen stated, "RISC chips could be a future threat to the VAX line," and suggested that the VAX team find ways to make VAX competitive with future RISC systems. This led to the formation of the "RISCy VAX" team, which considered various concepts, including a hybrid system that would combine VAX instruction sets with RISC-like behavior. However, such hybrid designs were concluded to introduce overhead and not be competitive with pure RISC machines.

A new idea, proposed by Nancy Kronenberg, suggested that "people use VMS, not VAX," and if only some hardware dependencies of VMS were preserved, VMS could be ported to a RISC chip. This idea was presented at a strategic task force meeting in February 1989, and two key questions were raised: "Could this RISC design deliver performance in the Unix market?" and "Should this machine be an open standard?" As a result, the PRISM architecture was modified to adopt a new concept called "EVAX," which was a follow-up to the successful CMOS CVAX implementation.

Alpha maintained most of the PRISM's basic concepts but was designed so that VMS and VMS programs could run at reasonable speeds without conversion. The major contribution of the Alpha architecture was not so much the architecture itself but its implementation. At the time (and still today), the microchip industry used automated design tools to create products, but DEC's chip designers pursued manual circuit design to handle the complexity of the VAX architecture. Alpha chips applied manual circuit design to a clean and simple architecture, allowing for higher operating frequencies and sparking a renaissance in chip design within the microprocessor design community.

The Alpha processor was initially designated the DECchip 21x64 series and was renamed "Alpha" in the mid-1990s. The name "DECchip" was derived from "21" representing the 21st century and "64" representing the 64-bit architecture. Internally, Alpha processors were identified by EV numbers, originally standing for "Extended VAX," but also humorously referencing "Electric Vlasic."

In May 1997, DEC filed a lawsuit claiming that Intel had infringed on Alpha patents used in Pentium, Pentium Pro, and Pentium II chips. To resolve this, DEC's chip design and manufacturing division, which included DEC's StrongARM implementation of the ARM architecture, was sold to Intel.