The Alpha 21264 Microprocessor Architecture

This document provides a technical overview of the 21264 Alpha microprocessor, the third generation in its product line. It details how the design achieves high performance through a combination of a fast 600 MHz cycle time and advanced micro-architectural features. Key aspects discussed include:

• Pipeline and Execution: The 21264 utilizes a super-scalar, out-of-order, and speculative execution pipeline.
• Branch Prediction: It features a sophisticated tournament branch prediction scheme that combines local and global history to maximize accuracy.
• Register Renaming: Implemented to eliminate unnecessary dependencies and support speculative execution.
• Memory System: A high-bandwidth memory system with on-chip and off-chip caches that manages multiple in-flight memory references.
• Cache Management: Includes specialized instructions for prefetching and cache management to improve data access efficiency.