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Intel VC820 Design Guide - Page 113

Post-Layout Simulation, 3.2.5.1 Intersymbol Interference, 3.2.5.2 Cross-Talk Analysis

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Advanced System Bus Design 3.2.5 3.2.5.1 3.2.5.2 3.2.5.3 Post-Layout Simulation Following layout, extract the interconnect information for the board from the CAD layout tools. Run simulations to verify that the layout meets timing and noise requirements. A small amount of "tuning" may be required; experience at Intel has shown that sensitivity analysis dramatically reduces the amount of tuning required. The post layout simulations should take into account the expected variation for all interconnect parameters. Intel specifies signal integrity at the device pads and therefore recommends running simulations at the device pads for signal quality. However, Intel specifies core timings at the device pins, so simulation results at the device pins should be used later to correlate simulation performance against actual system measurements. Intersymbol Interference Intersymbol Interference (ISI) refers to the distortion or change in the waveform shape caused by the voltage and transient energy on the network when the driver begins its next transition. Intersymbol Interference (ISI) occurs when transitions in the current cycle interfere with transitions in subsequent cycles. ISI can occur when the line is driven high, low, and then high in consecutive cycles (the opposite case is also valid). When the driver drives high on the first cycle and low on the second cycle, the signal may not settle to the minimum VOL before the next rising edge is driven. This results in improved flight times in the third cycle. Intel performed ISI simulations for the topology given in this section by comparing flight times for the first and third cycle. ISI effects do not necessarily span only 3 cycles so it may be necessary to simulate beyond 3 cycles for certain designs. After simulating and quantifying ISI effects, adjust the timing budget accordingly to take these conditions into consideration. Cross-Talk Analysis AGTL+ cross-talk simulations can consider the processor core package, Intel 82820 MCH package, and SC242 connectors as non-coupled. Treat the traces on the processor cartridge and baseboard as fully coupled for maximum cross-talk conditions. Simulate the traces as lossless for worst case cross-talk and lossy where more accuracy is needed. Evaluate both odd and even mode cross-talk conditions. AGTL+ Cross-talk simulation involves the following cases: • Intra-group AGTL+ cross-talk • Inter-group AGTL+ cross-talk • Non-AGTL+ to AGTL+ cross-talk Monte Carlo Analysis Perform a Monte Carlo analysis on the extracted baseboard. Vary all parameters recommended for the pre-layout Monte Carlo analysis within the region that they are expected to vary. The range for some parameters will be reduced compared to the pre-layout simulations. For example, baseboard lengths L1 through L7 should no longer vary across the full min and max range on the final baseboard design. Instead, baseboard lengths should now have an actual route, with a length tolerance specified by the baseboard fabrication manufacturer. Intel®820 Chipset Design Guide 3-13

Section	Page
Introduction 1	13
1.1 About This Design Guide	13
1.2 References	14
1.3 System Overview	14
1.3.1 Chipset Components	15
1.3.2 Bandwidth Summary	16
1.3.3 System Configuration	17
1.4 Platform Initiatives	20
1.4.1 Direct Rambus*	20
1.4.2 Streaming SIMD Extensions	20
1.4.3 AGP 2.0	20
1.4.4 Hub Interface	20
1.4.5 Manageability	21
1.4.6 AC’97	22
1.4.7 Low Pin Count (LPC) Interface	23
Layout/Routing Guidelines 2	27
2.1 General Recommendations	27
2.2 Component Quadrant Layout	27
2.3 Intel® 820 Chipset Component Placement	29
2.4 Core Chipset Routing Recommendations	30
2.5 Source Synchronous Strobing	31
2.6 Direct Rambus* Interface	33
2.6.1 Stackup	34
2.6.2 Direct Rambus* Layout Guidelines	34
2.6.2.1 RSL Routing	34
2.6.2.2 RSL Termination	37
2.6.2.3 Direct Rambus* Ground Plane Reference	39
2.6.2.4 Direct Rambus* Connector Compensation	40
2.6.2.5 RSL Signal Layer Alternation	46
2.6.2.6 Length Matching Methods	47
2.6.2.7 VIA Compensation	49
2.6.2.8 Length Matching & Via Compensation Example	49
2.6.3 Direct Rambus* Reference Voltage	51
2.6.4 High-speed CMOS Routing	51
2.6.4.1 SIO Routing	52
2.6.4.2 Suspend-to-RAM Shunt Transistor	52
2.6.5 Direct Rambus* Clock Routing	54
2.6.6 Direct Rambus* Design Checklist	54
2.7 AGP 2.0	57
2.7.1 AGP Interface Signal Groups	58
2.7.2 1X Timing Domain Routing Guidelines	59
2.7.3 2X/4X Timing Domain Routing Guidelines	59
2.7.4 AGP 2.0 Routing Summary	61
2.7.5 AGP Clock Routing	62
2.7.6 General AGP Routing Guidelines	62
2.7.7 VDDQ Generation and TYPEDET#	63
2.7.8 VREF Generation for AGP 2.0 (2X and 4X)	65
2.7.9 Compensation	67
2.7.10 AGP Pull-ups	67
2.7.10.1 AGP Signal Voltage Tolerance List	68
2.7.11 Motherboard / Add-in Card Interoperability	68
2.8 Hub Interface	69
2.8.1 Data Signals	70
2.8.2 Strobe Signals	70
2.8.3 HREF Generation/Distribution	70
2.8.4 Compensation	71
2.9 System Bus Design	72
2.9.1 100/133 MHz System Bus	72
2.9.2 System Bus Ground Plane Reference	73
2.10 S.E.C.C. 2 Grounding Retention Mechanism (GRM)	73
2.11 Processor CMOS Pullup Values	75
2.12 Additional Host Bus Guidelines	78
2.13 Ultra ATA/66	82
2.13.1 Ultra ATA/66 Detection	82
2.13.2 Ultra ATA/66 Cable Detection	83
2.13.3 Ultra ATA/66 Pullup/Pulldown Requirements	86
2.14 AC’97	87
2.14.1 AC’97 Signal Quality Requirements	89
2.14.2 AC’97 Motherboard Implementation	89
2.15 USB	91
2.16 ISA (82380AB)	92
2.16.1 ICH GPIO connected to 82380AB	92
2.16.2 Sub Class Code	92
2.17 IOAPIC Design Recommendation	92
2.18 SMBus/Alert Bus	93
2.19 PCI	93
2.20 RTC	93
2.20.1 RTC Crystal	94
2.20.2 External Capacitors	94
2.20.3 RTC Layout Considerations	95
2.20.4 RTC External Battery Connection	95
2.20.5 RTC External RTCRST Circuit	96
2.20.6 RTC Routing Guidelines	96
2.20.7 VBIAS DC Voltage and Noise Measurements	97
Advanced System Bus Design 3	101
3.1 Terminology and Definitions	101
3.2 AGTL+ Design Guidelines	104
3.2.1 Initial Timing Analysis	105
3.2.2 Determine General Topology, Layout, and Routing Desired	108
3.2.3 Pre-Layout Simulation	108
3.2.3.1 Methodology	108
3.2.3.2 Sensitivity Analysis	108
3.2.3.3 Monte Carlo Analysis	109
3.2.3.4 Simulation Criteria	109
3.2.4 Place and Route Board	110
3.2.4.1 Estimate Component To Component Spacing for AGTL+ Signals	110
3.2.4.2 Layout and Route Board	110
3.2.4.3 Host Clock Routing	112
3.2.4.4 APIC Data Bus Routing	112
3.2.5 Post-Layout Simulation	113
3.2.5.1 Intersymbol Interference	113
3.2.5.2 Cross-Talk Analysis	113
3.2.5.3 Monte Carlo Analysis	113
3.2.6 Validation	114
3.2.6.1 Measurements	114
3.2.6.2 Flight Time Simulation	114
3.2.6.3 Flight Time Hardware Validation	115
3.3 Theory	115
3.3.1 AGTL+	115
3.3.2 Timing Requirements	116
3.3.3 Cross-talk Theory	116
3.3.3.1 Potential Termination Cross-Talk Problems	118
3.4 More Details and Insight	119
3.4.1 Textbook Timing Equations	119
3.4.2 Effective Impedance and Tolerance/Variation	120
3.4.3 Power/Reference Planes, PCB Stackup, and High Frequency Decoupling	120
3.4.3.1 Power Distribution	120
3.4.3.2 Reference Planes and PCB Stackup	121
3.4.3.3 High Frequency Decoupling	122
3.4.3.4 SC242 Connector	123
3.4.4 Clock Routing	123
3.5 Definitions of Flight Time Measurements/ Corrections and Signal Quality	124
3.5.1 VREF Guardband	124
3.5.2 Ringback Levels	124
3.5.3 Overdrive Region	124
3.5.4 Flight Time Definition and Measurement	125
3.6 Conclusion	126
Clocking 4	129
4.1 Clock Generation	129
4.2 Component Placement and Interconnection Layout Requirements	134
4.2.1 14.318MHz Crystal to CK133	134
4.2.2 CK133 to DRCG	134
4.2.3 MCH to DRCG	135
4.2.4 DRCG to RDRAM Channel	136
4.2.5 Trace Length	136
4.3 DRCG Impedance Matching Circuit	138
4.3.1 DRCG Layout Example	139
4.4 AGP Clock Routing Guidelines	139
4.5 Series Termination Resistors for CK133 Clock Outputs	139
4.6 Unused Outputs	140
4.7 Decoupling Recommendation for CK133 and DRCG	140
4.8 DRCG Frequency Selection and the DRCG+	140
4.8.1 DRCG Frequency Selection Table and Jitter Specification	140
4.8.2 DRCG+ Frequency Selection Schematic	141
System Manufacturing 5	145
5.1 In Circuit FWH Flash BIOS Programming	145
5.2 FWH Flash BIOS Vpp Design Guidelines	145
5.3 Stackup Requirement	145
5.3.1 Overview	145
5.3.2 PCB Materials	146
5.3.3 Design Process	146
5.3.4 Test Coupon Design Guidelines	147
5.3.5 Recommended Stackup	147
5.3.6 Inner Layer Routing	147
5.3.7 Impedance Calculation Tools	148
5.3.8 Testing Board Impedance	148
5.3.9 Board Impedance/Stackup Summary	149
System Design Considerations 6	153
6.1 Power Delivery	153
6.1.1 Terminology and Definitions	153
6.1.2 Intel® 820 Chipset Customer Reference Board Power Delivery	154
6.1.3 64/72Mbit RDRAM Excessive Power Consumption	157
6.1.3.1 Option 1: Reduce the Clock Frequency During Initialization	158
6.1.3.2 Option 2: Increase the Current Capability of the 2.5V Voltage Regulator	158
6.2 Power Plane Splits	159
6.3 Thermal Design Power	159
6.4 Glue Chip 3 (Intel® 820 Chipset Glue Chip)	160
Appendix A: Reference Board Schematics: Uni-Processor	161
Reference Design Schematics: Uni-Processor A	163
Appendix B: Reference Design Schematics: Dual-Processor B	201

Match case Limit results 1 per page

Intel

820 Chipset

Design Guide

3-13

Advanced System Bus Design

3.2.5

Post-Layout Simulation

Following layout, extract the interconnect information for the board from the CAD layout tools.

Run simulations to verify that the layout meets timing and noise requirements. A small amount of

“tuning” may be required; experience at Intel has shown that sensitivity analysis dramatically

reduces the amount of tuning required. The post layout simulations should take into account the

expected variation for all interconnect parameters.

Intel specifies signal integrity

at the device pads

and therefore recommends running simulations at

the device pads for signal quality. However, Intel specifies core timings

at the device pins,

simulation results at the device pins should be used later to correlate simulation performance

against actual system measurements.

3.2.5.1

Intersymbol Interference

Intersymbol Interference (ISI) refers to the distortion or change in the waveform shape caused by

the voltage and transient energy on the network when the driver begins its next transition.

Intersymbol Interference (ISI) occurs when transitions in the current cycle interfere with transitions

in subsequent cycles. ISI can occur when the line is driven high, low, and then high in consecutive

cycles (the opposite case is also valid). When the driver drives high on the first cycle and low on

the second cycle, the signal may not settle to the minimum V

before the next rising edge is driven.

This results in improved flight times in the third cycle. Intel performed ISI simulations for the

topology given in this section by comparing flight times for the first and third cycle. ISI effects do

not necessarily span only 3 cycles so it may be necessary to simulate beyond 3 cycles for certain

designs. After simulating and quantifying ISI effects, adjust the timing budget accordingly to take

these conditions into consideration.

3.2.5.2

Cross-Talk Analysis

AGTL+ cross-talk simulations can consider the processor core package, Intel 82820 MCH

package, and SC242 connectors as non-coupled. Treat the traces on the

processor cartridge and

baseboard as fully coupled for maximum cross-talk conditions. Simulate the traces as lossless for

worst case cross-talk and lossy where more accuracy is needed. Evaluate both odd and even mode

cross-talk conditions.

AGTL+ Cross-talk simulation involves the following cases:

•

Intra-group AGTL+ cross-talk

•

Inter-group AGTL+ cross-talk

•

Non-AGTL+ to AGTL+ cross-talk

3.2.5.3

Monte Carlo Analysis

Perform a Monte Carlo analysis on the extracted baseboard. Vary all parameters recommended for

the pre-layout Monte Carlo analysis within the region that they are expected to vary. The range for

some parameters will be reduced compared to the pre-layout simulations. For example, baseboard

lengths L1 through L7 should no longer vary across the full min and max range on the final

baseboard design. Instead, baseboard lengths should now have an actual route, with a length

tolerance specified by the baseboard fabrication manufacturer.