Data Flow Architectures

1. CSE539: Advanced Computer Architecture
Chapter 9
…Dataflow Architectures
Book: “Advanced Computer Architecture – Parallelism, Scalability, Programmability”, Hwang & Jotwani
Sumit Mittu
Assistant Professor, CSE/IT
Lovely Professional University
sumit.12735@lpu.co.in

2. In this chapter…
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Evolution of Dataflow Computers
Dataflow Graphs
Static v/s Dynamic Data Flow Computers
Pure Dataflow Machines
Explicit Token Store Machines
Hybrid and Unified Architectures
Dataflow v/s Control flow Computers
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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3. DATAFLOW AND HYBRID ARCHITECTURES
• Data-driven machines
• Evolution of Dataflow Machines
• Dataflow Graphs
o Dataflow Graphs examples.
o Activity Templates and Activity Store
o Example: dataflow graph for cos x
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+
𝒙𝟒
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−
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o More examples
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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4. DATAFLOW AND HYBRID ARCHITECTURES
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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5. DATAFLOW AND HYBRID ARCHITECTURES
• Static Dataflow Computers
o Special Feedback Acknowledge Signals between nodes
o Firing Rule:
• A node is enabled as soon as tokens are present on all input arcs and there is no token on
any of its output arc
o Example: Dennis Machine (1974)
• Dynamic Dataflow Computers
o Tagged Tokens
o Firing Rule:
• A node is enabled as soon as tokens with identical tags are present at each of its input arcs
o Example: MIT Tagged Token Dataflow Architecture (TTDA) machine (just simulation, never built)
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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6. DATAFLOW AND HYBRID ARCHITECTURES
• Diagrams of static dataflow and dynamic dataflow
• from Hwang and Briggs….
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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7. DATAFLOW AND HYBRID ARCHITECTURES
• Pure Dataflow Machines
o TTDA (1983)
• TTDA was simulated but never built
o Manchester Dataflow Computer (1982)
• Operated asynchronously using a separate clock for each PE
o ETL Sigma-1 (1987)
• 128 PEs fully synchronous with a 10-Mhz clock
• Implemented I-structured memory proposed in TTDA
• Lacked High Level Languages for users
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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8. DATAFLOW AND HYBRID ARCHITECTURES
• Explicit Token Store Machines
o Eliminate associative token matching.
o Waiting token memory is directly accessed using full/empty bits.
o Examples
• MIT/Motorola Monsoon (proposed 1988; operational 1991)
o Multithreading support
o 8 processors
o 8 I-structure memory modules
o 8x8 crossbar network
• ETL EM-4 (1989)
o Extension of Sigma-1
o Proposed 1024 nodes; Operational Implementation 80 nodes
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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9. DATAFLOW AND HYBRID ARCHITECTURES
• Hybrid and Unified Architectures
o Combining Features of von-Neumann and Dataflow architectures
o Examples:
• MIT P-RISC (1988)
• IBM Empire (1991)
• MIT/Motorola *T (1991)
o “RISC-ified” dataflow architecture
• Implemented in P-RISC
• Splitting complex dataflow instructions into separate simple component instructions
• Tighter encoding and longer threads for better performance
• Dataflow Processing v/s Control Flow Processing
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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10. DATAFLOW AND HYBRID ARCHITECTURES
• Computing ab + a/c with:
(a) control flow; (b) dataflow. Pure dataflow basic execution pipeline: (c) single-token-per-arc dataflow;
(d) tagged-token dataflow; (e) explicit token store dataflow
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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11. DATAFLOW AND HYBRID ARCHITECTURES
• Computing ab + a/c with:
(a) control flow; (b) dataflow. Pure dataflow basic execution pipeline: (c) single-token-per-arc dataflow;
(d) tagged-token dataflow; (e) explicit token store dataflow
Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University
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