PALcode for Alpha Microprocessors System Design Guide

This System Design Guide explains how to use and customize the Privileged Architecture Library code (PALcode) for Alpha Microprocessors, specifically models 21064, 21064A, 21066, 21066A, 21068, and 21164.

PALcode is a critical layer of low-level software that bridges the hardware and the operating system. It performs essential functions that are impractical for hardware or the OS to handle directly, such as power-up initialization, memory management (including translation buffer fills), interrupt and exception dispatching, privileged instructions, atomic operations, and instruction emulation.

The document details:

• PALcode Fundamentals: How PALcode operates in a special, privileged environment called PALmode (disabling interrupts and memory mapping, enabling reserved opcodes for low-level hardware access).
• Invocation: How PALcode is invoked by both hardware events (e.g., reset, system errors, interrupts, memory-management faults) and software via CALL_PAL instructions.
• Product & Development: It introduces the Evaluation Board Software Developer's Kit (EBSDK) PALcode as a customizable sample. It outlines the build process (pre-processing, assembly, linking) and the use of the PALcode Violation Checker (pvc) tool to ensure compliance with design rules.
• Customization Aspects: System designers can modify PALcode to tailor it to specific hardware and software needs, covering areas like backup cache configuration, interrupt/exception handling, new CALL_PAL functions, and memory management policies.
• Integration with Evaluation Board: The guide explains how PALcode interacts with the Evaluation Board's SROM (Serial ROM) and Debug Monitor during the bootstrap process, including the creation of bootable images using the Sysgen utility.
• Key EBSDK PALcode Features: Support for I/O, basic interrupt processing (timer, system error, device), virtual and physical memory mapping, and a list of console service functions for interacting with internal processor registers.

The guide is intended for system designers and implementors who need to modify PALcode for Alpha microprocessor-based system designs, particularly within a Digital UNIX or similar environment.