19+-+Interconnect

19+-+Interconnect - CS 4290/6290 Interconnect On-chip...

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CS 4290/6290 Interconnect
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On-chip Networks (OCNs) Sometimes called network-on- chip (NoC) System/Storage-area Networks (SANs) For multi-processor/multi- computer systems, and server-I/ O connections Local Area Networks (LANs) 100’s-1000’s of nodes; typically up to a few km of distance; usually Ethernet up to 10Gbps Wide Area Networks (WANs) Also called long-haul networks; global-scale; e.g., ATM (asynchronous transfer mode) CS 4290/6290 – Spring 2009 – Prof. Milos Prvulovic nodes 2
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Traditionally just used a bus Not scalable For massive MP systems, used more generalized (switched) networks These are moving into commodity systems • E.g., AMD Opteron’s Hypertransport Also used for the Internet Embedded systems will likely use them/already use them in limited forms CS 4290/6290 – Spring 2009 – Prof. Milos Prvulovic 3
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CS 4290/6290 – Spring 2009 – Prof. Milos Prvulovic Classification: Shared Medium or Switched 4
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CS 4290/6290 – Spring 2009 – Prof. Milos Prvulovic Need arbitration to decide who gets to talk Arbitration can be centralized or distributed Centralized not used much for networks Special arbiter device (or must elect arbiter) Good performance if arbiter far away? Nah. Distributed arbitration Check if media already used (carrier sensing) If media not used now, start sending Check if another also sending (collision detection) If collision, wait for a while and retry “For a while” is random (otherwise collisions repeat forever) Exponential back-off to avoid wasting bandwidth on collisions 5
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CS 4290/6290 – Spring 2009 – Prof. Milos Prvulovic Need switches Introduces switching overheads No time wasted on arbitration and collisions Multiple transfers can be in progress If they use different links, of course Circuit or Packet Switching Circuit switching: end-to-end connections Reserves links for a connection (e.g., phone network) Packet switching: each packet routed separately Links used only when data transferred (e.g., Internet Protocol) 6
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CS 4290/6290 – Spring 2009 – Prof. Milos Prvulovic
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This note was uploaded on 04/12/2010 for the course CS 6290 taught by Professor Staff during the Spring '08 term at Georgia Tech.

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19+-+Interconnect - CS 4290/6290 Interconnect On-chip...

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