Alpha Assembly Language Guide
Randal E. Bryant · 1998
This document provides an overview of the Alpha instruction set and assembly language programming conventions. The Alpha architecture was formulated by Digital Equipment Corporation as a second generation reduced instruction set computer (RISC) architecture. It represents a careful balance between providing a sufficient range of instructions to encode common operations while avoiding a lot of features that could slow down the machine or lead to implementation difficulties in the future. Digital Equipment Corporation was subsequently acquired by Compaq in the Summer of 1998. Compaq is continuing to support Alpha. More complete documentation is available from Digital/Compaq [1, 2]. 1.1. Data Types The most notable feature of the Alpha is that it is a true 64-bit machine. All integer registers are 64 bits wide. Manipulating 64-bit addresses and 64-bit integers is fully supported. In addition, there is support for 32-bit integers. For historical reasons, (dating back to the PDP-11, a 16-bit machine), Digital had an idiosyncratic terminology for word sizes. They consider a “word ” to be 16-bits. Based on this, they refer to 32-bit