Mescal Communication Channel Model

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Mescal Communication Channel Model

• Xinping Zhu
• Princeton University
• December,15,2000

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Motivation

• Design Exploration Environment Need On-Chip
  Communication Channel Modelling
• Divide/Conquer Mescal Communication Architecture
  is composed of communication assist and
  communication channel model.
• How to cover the whole picture of various
  paradigms of existing and novel communication
  channels using object-oriented software modeling?
• e.g. Synchronous Data Bus such as CoreConnect
  Bus from IBM
• Dedicated point to point circuit link
• Optical (WDMA) Bus

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Previous Work

• Ad-hoc Approaches to model the communication
  network
• HDL approach
• e.g. IBM provides Verilog description of
  CoreConnect Bus to help designers to choose
  different parameters to tune the performance of
  the bus design.
• C library approach
• Using different C library calls to model
  communication library call on top of different
  type of communication network. Popular in the
  implementation of C-based parallel simulation
  environment.
• O-O approach
• Model one specific type of communication channel
  technology using O-O based software modelling
  tools.
• e.g. Modelling CoreConnect Bus by extending some
  generic bus modules

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Systematic Approach

• Why a systematic approach is needed?
• Design exploration need systematic coverage of
  almost every kind of existing communication
  channels.
• Every communication channel seems drastically
  different.
• e.g. Packet-switching network and circuit
  switching dont go together.
• They also share some common features
• e.g.
• All bus system has the so called
  Master-Arbiter scheme.
• Similarity between AMBA bus and CoreConnect
  Bus
• They obey the same interface to communicate with
  communication assists.
• What is the modelling strategy?

Tree-like Object Inheritance Hierarchy !
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Mescal Communication Channel Modelling
Hierarchy(Proposed)
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Mescal Communication Channel Modelling Hierarchy
(cont)
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Mescal Communication Channel Modelling Strategy
(A Systematic Approach)

• Actor inheritance is designed to accommodate the
  most intrinsic abstract properties of various
  communication channel models.
• Flexible enough to model common existing channel
  model paradigms and future designs.
• Software reusability is considered throughout the
  design flow.
• Interfacing with Mescal Communication Assist and
  Mescal Processing Element to consist the whole
  Mescal design exploration environment.

GUI Interface for Communication Channel Modelling
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Unicast model

• One important kind of channel is the so called
  unicast model
• Defination One data packet can only traverse to
  one destination.
• The channel model knows exactly the topology
• It query the neighbor's addresses upon
  initialization or topological mutation and
  building the corresponding routing table.
• Routing the incoming data packet referring the
  routing table.
• Can be used to construct more complex
  point-to-point style communication network
• e.g.
• SwitchBar, Multistage Network

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Generic Bus Model

• Bus may be the most understandable
  interconnecting pattern
• Modelling, on the contrary, is not easy
• Complex and incompatible protocols
• e.g. CoreConnect Bus specification goes 100
  pages and around 100 different pins names.
• Extracting the most essential properties of a bus
  system which can be fairly easily adapted for
  future use.
• Goal by extending generic bus architecture, we
  can get a CoreConnect-like bus model.

• How generic is generic ? Design Tradeoffs
• Synchronous transaction
• Centralized parallel arbitration
• Separate data and control lines
• Or just add more layers in the inheritance tree?

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Ongoing work

• Implementing the bus model
• Tradeoff in selecting different bus construction
  methods
• How to make it more extensible?
• Standalone testing environment
• Poisson source served as excitation
• Interfacing with Mescal CA model
• Channel receiver and transmitter obey the same
  port and semantic convention.