hyper transport

7/31/2019 Hyper Transport

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CONTENTS

Need for Hyper Transport Technology

Definition of Hyper Transport Technology

Foundation of Hyper Transport Technology

Multiple Topology

Hyper Transport Technology

Command/Address/Data packet protocols

Hyper Transport Packet Format

A Low Latency Solution

Conclusion


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NEED

Unrealistic and expensive both in actual costs andpower consumption.

Wider buses for higher performance throughhigher bandwidth.

Due to ever shrinking desktop and server formfactors required by IT.


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Signaling Basics

1.Differential signaling.

2.Use of advanced LVDS.

Flexibility Scalability

Adoption

Networking Extensions

1.Message Passing Protocol2.Error Recovery Protocol

3.Supports Peer-To-Peer Transfer

4.Support for 64 bit Address

Foundation of Hyper Transport

Technology


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MULTIPLE TOPOLOGIES

Daisy chain topology- HTT Tunneling makes daisy chains unto 31independent devices

Switch Topology- HTT Switch is designed for use in latencysensitive environment supporting multiple processes.

Star Topology- Distributes HTT links in a spoke fashion.


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Topology (Daisy chain)


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Topology (Switch)


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TOPOLOGY (STAR)


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Hyper Transport Technologies

Support for Multiple Packages

Easier to Layout

Electrical Considerations

Signal Routing

Reduction of Electrical Noise Better Grounding

Other Issues


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Supports for Multiple PackagesHTT uses Flip-Chip

Package.

BENEFITS ARE: Lower inductance

power Connection.

Reduced inductanceand capacitance on

the signals.


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Easier to Layout SKEW is caused due

to path difference in

different paths.

With the use of an

independent clock for

every grouping of 8LVDS signals, SKEW

is reduced

significantly.


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The Hyper Transport link uses balanced LVDS lines. Signal voltage on eac

wire line is symmetrical and of opposite polarity, ensuring the highest noise

immunity.

Electrical Considerations


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Signal RoutingAGP was designed with two

purposes:

1. To relieve the PCI bus ofwork with graphics data.

2. To facilitate better bandwidthwithin the video system.

HTT has advantages:

1. Is faster than AGP.2. Has smaller matching

requirements.

3. Is far easier to implement.


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Reduction of Electrical Noise

Figure shows crosstalk

due to

electrical/magnetic field

affecting the signals ofadjacent links in PCI

buses

By the use of

differential signalingused in HTT,crosstalk is

reduced.


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BETTER GROUNDING

It has three links-

true, complement

and ground.

Complementary link

can be used as

secondary link when

required.


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OTHER ISSUES

EMI Elimination

Easier To Power

ON-Chip Termination


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The Hyper Transport dual, point-to-pointunidirectional links include a data path, one ormore clock signals and a single control line.

Commands, Address and Data are carried inpackets over the data path.

System level control lines RESET# andPWROK complete the required set of signallines



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The Hyper Transport link consists of a set of command/address/data (CAD) lines, one control line per link, and oneclock line per eight bits of CAD.



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Hyper Transport control packets consist typically of 4 to 8 bytes ofcommand information. With optional 64-bit extended addressing, controlpackets can be 12 bytes. Data packets consist of 4- to 64-byte datapayloads (in increments of 4 bytes) and directly follow either (1) an 8-byte read request followed by a 4-byte read response or (2) an 8-bytewrite request control packet.


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Hyper Transport reads and writes are very low overhead. Writes require

only an 8-byte Write Request control packet followed by the data

packet. Reads require an 8-byte Read Request control packet, followed

by a 4-byte Read Response packet from the receiver, followed by the

actual read data packet.



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Hyper Transport, focused on creating a

unified chip-to-chip communicationschannel that exhibits

Lowest possible latency.

Lowest possible overhead in

supporting packet-based data streams.

Priority Request Interleaving (PRI)

Low-latency Solution


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Packet overhead comparison between Hyper Transport and PCI Express.

Low-latency Solution


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PRIORITY REQUEST INTERLEAVING(PRI)


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CONCLUSION

The tunneling capability enables up to 31 devices to be connectedin a chain.

The use of enhance low - voltage differential signaling helps toeliminate many of the problems associated with single-endedsignaling, including crosstalk and EMI.

Hyper Transport technology extends the lifespan of PCI byproviding full backwards compatibility for PCI software, drivers,and operating systems while eliminating bottlenecks andproviding the bandwidth necessary for future high - speed chipsand interconnect standards.

Support for asymmetrically links and scalability in speed, width,frequency, and direction allows system designers to have theflexibility to trade performance for cost and power savings whereit is appropriate.

Hyper Transport technology extends the lifespan of devices byproviding enough bandwidth headroom to allow system designersto add new high performance parts.


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ThankYou

hyper transport

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