
xxviii
MPC603e & EC603e RISC Microprocessors User's Manual
MOTOROLA
This document summarizes features of the 603e that are not defined by the architecture.
This document and
The Programming Environments Manual
distinguish between the three
levels, or programming environments, of the PowerPC architecture, which are as follows:
PowerPC user instruction set architecture (UISA)—The UISA defines the level of
the architecture to which user-level software should conform. The UISA defines the
base user-level instruction set, user-level registers, data types, memory conventions,
and the memory and programming models seen by application programmers.
PowerPC virtual environment architecture (VEA)—The VEA, which is the smallest
component of the PowerPC architecture, defines additional user-level functionality
that falls outside typical user-level software requirements. The VEA describes the
memory model for an environment in which multiple processors or other devices can
access external memory, defines aspects of the cache model and cache control
instructions from a user-level perspective. The resources defined by the VEA are
particularly useful for optimizing memory accesses and for managing resources in
an environment in which other processors and other devices can access external
memory.
PowerPC operating environment architecture (OEA)—The OEA defines supervisor-
level resources typically required by an operating system. The OEA defines the
PowerPC memory management model, supervisor-level registers, and the exception
model.
Implementations that conform to the PowerPC OEA also conform to the PowerPC
UISA and VEA.
It is important to note that some resources are defined more generally at one level in the
architecture and more specifically at another. For example, conditions that cause a floating-
point exception are defined by the UISA, while the exception mechanism itself is defined
by the OEA.
Because it is important to distinguish between the levels of the architecture in order to
ensure compatibility across multiple platforms, those distinctions are shown clearly
throughout this book.
For ease in reference, this book has arranged topics described by the architecture into topics
that build upon one another, beginning with a description and complete summary of 603e-
specific registers and progressing to more specialized topics such as 603e-specific details
regarding the cache, exception, and memory management models. As such, chapters may
include information from multiple levels of the architecture. (For example, the discussion
of the cache model uses information from both the VEA and the OEA.)
The PowerPC Architecture: A Specification for a New Family of RISC Processors
defines
the architecture from the perspective of the three programming environments and remains
the defining document for the PowerPC architecture.
The information in this book is subject to change without notice, as described in the
disclaimers on the title page of this book. As with any technical documentation, it is the