Accelerated Graphics Port Interface Specification

AGP3.0 Interface Specification

Rev. 1.0

1 Introduction and Overview

The AGP V3.0 Interface Specification (or AGP3.0) describes enhancements to the Accelerated

Graphics Port (AGP) Interface. AGP3.0 offers a significant increase in performance along with feature

enhancements to AGP2.0. This interface represents the natural evolution from the existing AGP to meet

the ever-increasing demands placed on the graphic interfaces within the workstation and desktop

environments.

While AGP3.0 clearly represents an evolutionary step in the AGP roadmap, it is not a superset of all

previous interface versions. Certain AGP2.0 features are no longer supported by AGP3.0. Table 1

shows the evolution of the interface in terms of major specification releases.

Table 1: AGP Specification Releases

AGP1.0 AGP2.0 AGP3.0

Signaling 3.3V signaling 1.5V Signaling New 0.8V Signaling

Protocol Pipelined transactions +

Source synchronous

clocking

AGP1.0 + Fast Writes AGP2.0 + Some

enhancements – some

deletions (See Sec

1.5.1)

Speeds 2X, 1X 4X, 2X, 1X 8X, 4X

Connector 3.3V keyed 1.5V keyed, Universal 1.5V keyed, Universal

Throughout this document, the terms AGP1X, AGP2X, AGP4X, and AGP8X refer to the speed of data

transfers on the AGP Interface while AGP1.0, AGP2.0, and AGP3.0 refer to specific releases of the AGP

Interface specifications.

1.1 Organization of This Document

This document is to be used in conjunction with the AGP2.0 Interface Specification. Therefore, the

focus will be on changes and additions made to that specification. The organization is as follows:

1. Chapter 1: Provides an introduction to the changes and enhancements made to the existing

AGP interface specification.

2. Chapter 2: Describes changes and enhancements that apply to both desktop and workstation

class platforms. Topics covering all changes include protocol and transactions, signal interface,

platform dependencies, and programming.

3. Chapter 3: Provides the electrical and physical design specifications.

These three chapters complete the main body of the specification and are also referred to as the core

specification. Several appendices describe additional changes and/or enhancements that generally

target Workstation platforms. These are described as follows:

1. Appendix A: Describes optional features such as isochronous streaming protocol, further

enhancements to flow control, etc.

2. Appendix B: Includes the optional programming enhancements that would be needed to support

the features discussed in Appendix A: Workstation Enhancements.