Gecko's CPU Library

DEC Alpha 21164A (EV56) processors

Introduction: October 1995

21164A (EV56) was introduced at a Microprocessor Forum in October of 1995. It was a modified release of EV5 after a redesign for a proprietary 4-layer 0.35µ CMOS6 process. It was manufactured at the same semiconductor factory in Hudson (Massachusetts, the USA), and DEC had invested about 450M USD in modernisation prior to. The most important architectural difference was BWX (Byte-Word Extension) - a set of 6 additional instructions to load/store data in 8- or 16-bit quanta (LDBU, LDWU, STB, STW, SEXTB, SEXTW). Right from the start, the Alpha architecture was forced to load/store data in 32- or 64-bit quanta what caused certain difficulties while porting or emulating code belonging to other processor architectures such as i386 or MIPS. A request to implement BWX in hardware was submitted in June of 1994 by Richard Sites and was approved in June of 1995. Although to perform BWX transfers a system logic had to be aware of it as well. Core frequencies of 21164A (EV56) ranged from 366MHz to 666MHz (TDP from 31W to 55W), and the manufacturing started somewhere in the summer of 1996. Also was produced by Samsung under a licence agreement signed in June of 1996 (a 666MHz version was available from Samsung only). Consisted of 9.66M transistors, possessed a die size of 209mm², required a dual voltage power supply (2.5V for primary and 3.3V for input/output circuits).