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

In this chapter…

• 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 2

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 3

• 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

• 𝐜𝐨𝐬 𝐱 ≅ 𝟏 − 𝒙𝟐

𝟐!+

𝒙𝟒

𝟒! −

𝒙𝟔

𝟔!

o More examples

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 4

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 5

• 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)

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 6

• Diagrams of static dataflow and dynamic dataflow

• from Hwang and Briggs….

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 7

• 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

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 8

• 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

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 9

• 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

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 10

• 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

DATAFLOW AND HYBRID ARCHITECTURES

Sumit Mittu, Assistant Professor, CSE/IT, Lovely Professional University 11

• 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