alpha processor

The Alpha processors are a 64-bit microprocessor family from Digital Equipment(DEC) with the product designations 21x64: 21064, 21164, 21264 and 21364.

The history of the Alpha processors

The first microprocessor in this family was the 21064 with clock frequencies ranging from 150 MHz to 275 MHz. The 21064 has a structure track width of 0.5 µm, 1.6 million transistors and a SPEC-definedcomputing power for SPECint of 2 (A version: 4) and for floating point calculations SPECfp of 2 (5). The level 1 caches for data and addresses were 8 KB in size, 16 kilobytes (KB) each for the A version.

The 21164 introduced in 1994 already had 9.3 million transistors in 0.35 µm technology. It consists of an instruction, integer, floating point and memory unit. The computing power was increased for integer calculations SPECint to 13, in the A version to 18, and that for floating point calculations SPECfp to 18, respectively 27. This corresponds to a computing power of 1700 (2400) MIPS. The 21164 is a superscalar processor with clock frequencies from 266 MHz to 600 MHz (A version), level 1 caches of 2 x 8 KB and a level 2 cache of 96 KB.

In the further development, the 21264, 156 registers and Level 1 caches with 64 KB each for data and addresses, clock rates of 600 MHz and 1 GHz and 15.2 million transistors in conjunction with pipelining ensure computing performances of 30 for SPECint and >50 for SPECfp. In terms of integration density, the 21264 implements ELSI technology with a structure track width of 0.18 µm and the 15.2 million transistors. The throughput rates on the Level 2 and Level 3 caches are 4 GB/s to 5.5 GB/s with the EV68 protocol. The 21264 EV68 has 590 connection pins.

The later generations of Alpha processors

The following generation of the 21364/EV7 is based on a structure track width of 0.18 µm and has over 100 million transistors. The clock rate is 1.3 GHz, the data throughput is 16 GB/s. The 21364 has a level 1 cache of 128 KB, a level 2 cache of 1.5 megabytes( MB) and 1440 connections. It requires a power of 100 W. Power ratings are 70 for SPECint95 and 120 for SPECfp95.

Alpha processors operate on the system bus with specially developed protocols, the EV protocols(EV5, EV6, EV7, EV56, ...), which also support multiprocessor systems. The EV protocols provide point-to-point connections and transmit the 64 bits on each edge, as with the DDR method, or four times per clock pulse, as with the QDR method. For example, this results in a data throughput of 1.6 GB/s for EV7 with two transfers per clock pulse at a clock frequency of 100 MHz.

Alpha processors are particularly suitable for business-critical applications such as customer relationship management( CRM), data mining and data warehousing, e-commerce and for technical and scientific applications.