Intel® 820E Chipset

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Term

Definition

 

 

Simultaneous

Difference in electrical timing parameters and degradation in signal quality caused

switching

by multiple signal outputs simultaneously switching voltage levels (e.g., high to

output (SSO)

low), in the direction opposite to a single signal (e.g., low to high) or in the same

effects

direction (e.g., high to low). These are respectively called odd-mode switching and

 

even-mode switching. This simultaneous switching of multiple outputs creates

 

higher current swings that may cause additional propagation delay (or “push-out”)

 

or a decrease in propagation delay (or “pull-in”). These SSO effects may affect the

 

setup and/or hold times and are not always taken into account by simulations.

 

System timing budgets should include margin for SSO effects.

Stub

Branch from the trunk terminating at the pad of an agent

 

 

Test load

Intel uses a 50 Ω test load for specifying its components.

 

 

Trunk

The main connection, excluding interconnect branches, terminating at agent pads

 

 

Undershoot

Maximum voltage a signal may extend below VSS at the processor core pad. See the

 

respective processor’s datasheet for the undershoot specifications.

Victim

A network that receives a coupled crosstalk signal from another network is called

 

the victim network.

VREF guard

A guard band (∆VREF) defined above and below VREF, to provide a more realistic

band

model accounting for noise, such as crosstalk, VTT noise, and VREF noise

3.2.AGTL+ Design Guidelines

The following step-by-step guideline was developed for systems based on two processor loads and one Intel 82820 MCH load. Systems using custom chipsets will require timing analysis and analog simulations specific to those components.

The guideline recommended in this section is based on experience accumulated at Intel while developing many different systems based on the Intel® Pentium® Pro processor family and the Pentium III processor. First, perform an initial timing analysis and topology definition. Then perform pre-layout analog simulations, for a detailed picture of a working “solution space” for the design. These pre-layout simulations help define the routing rules prior to placement and routing. After routing, extract the interconnect database and perform post-layout simulations to refine the timing and signal integrity analysis. Validate the analog simulations when actual systems become available. The validation section describes a method for determining the flight time in the actual system.

Guideline Methodology

Initial timing analysis

Determine general topology, layout, and routing.

Pre-layout simulation

Sensitivity sweep

Monte Carlo Analysis

Place and route board

Estimate component-to-component spacing for AGTL+ signals.

Lay out and route board.

Post-layout simulation

Interconnect extraction

Intersymbol interference (ISI), crosstalk, and Monte Carlo Analysis

Validation

Measurements

Determining flight time

Design Guide

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Image 141
Intel 820E manual AGTL+ Design Guidelines, Guideline Methodology