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). It was introduced as the DECchip 21064 before it was renamed in 1994. The 21064 is also known by its code name, EV4. It was announced in February 1992 with volume availability in September 1992. The 21064 was the first commercial implementation of the Alpha ISA, and the first microprocessor from Digital to be available commercially. It was succeeded by a derivative, the Alpha 21064A in October 1993. This last version was replaced by the Alpha 21164 in 1995. The first Alpha processor was a test chip codenamed EV3. This test chip was fabricated using Digital's 1.0-micrometre (μm) CMOS-3 process. The test chip lacked a floating point unit and only had 1 KB caches. The test chip was used to confirm the operation of the aggressive circuit design techniques. The test chip, along with simulators and emulators, was also used to bring up firmware and the various operating systems that the company supported. The production chip, codenamed EV4, was fabricated using Digital's 0.75 μm CMOS-4 process. Dirk Meyer and Edward McLellan were the micro-architects. Ed designed the issue logic while Dirk designed the other major blocks. Jim Montanaro led the circuit implementation. The EV3 was used in the Alpha Demonstration Unit (ADU), a multiprocessor system used by Digital to develop software for the Alpha platform before the availability of EV4 parts. The 21064 was unveiled at the 39th International Solid-State Circuits Conference (ISSCC) in mid-February 1992. It was announced on 25 February 1992, with a 150 MHz sample introduced on the same day. It was priced at $3,375 in quantities of 100,$1,650 in quantities between 100 and 1,000, and $1,560 for quantities over 1,000. Volume shipments began in September 1992. In early February 1993, the price of the 150 MHz version was reduced to$1,096 from $1,559 in quantities greater than 1,000.