Alpha 21364

The Alpha 21364, code-named "Marvel", also known as EV7 is a microprocessor developed by Digital Equipment Corporation (DEC), later Compaq Computer Corporation, that implemented the Alpha instruction set architecture (ISA). The Alpha 21364 was revealed in October 1998 by Compaq at the 11th Annual Microprocessor Forum, where it was described as an Alpha 21264 with a 1.5 MB 6-way set-associative on-die secondary cache, an integrated Direct Rambus DRAM memory controller and an integrated network controller for connecting to other microprocessors. Changes to the Alpha 21264 core included a larger victim buffer, which was quadrupled in capacity to 32 entries, 16 for the Dcache and 16 for the Scache. It was reported by the Microprocessor Report that Compaq considered implementing minor changes to branch predictor to improve branch prediction accuracy and doubling the miss buffer in capacity to 16 entries instead of 8 in the Alpha 21264. It was expected to be taped-out in late 1999, with samples available in early 2000 and volume shipments in late 2000. However, the original schedule was delayed, with the tape-out in April 2001 instead of late 1999. The Alpha 21364 was introduced on 20 January 2002 when systems using the microprocessor debuted. It operated at 1.25 GHz, but production models in the AlphaServer ES47, ES80 and GS1280 operated at 1.0 GHz or 1.15 GHz. Unlike previous Alpha microprocessors, the Alpha 21364 was not sold on the open market. The Alpha 21364 was originally intended to be succeeded by the Alpha 21464, code-named EV8, a new implementation of the Alpha ISA with four-way simultaneous multithreading (SMT). It was first presented in October 1999 at the 12th Annual Microprocessor Forum, but was cancelled on 25 June 2001 at a late stage of development. The development of the Alpha 21364 was most focused on features that would improve memory performance and multiprocessor scalability. The focus on memory performance was the result of a forward-looking article published in Microprocessor Report titled, "It's the Memory, Stupid!" written by Richard L.