Mini Project- Dual Processor Computation

Mini Project – Dual Processor Computation
Author: University of Hertfordshire
Date created:
Date revised: 2009
Abstract
The following resources come from the 2009/10 BEng in Digital Systems and Computer Engineering (course number 2ELE0065) from the University of Hertfordshire. All the mini projects are designed as level two modules of the undergraduate programmes.
The objectives of this module are to demonstrate, within an embedded development environment:
Processor – to – processor communication
Multiple processors to perform one computation task using parallel processing
This project requires the establishment of a communication protocol between two 68000-based microcomputer systems. Using ‘C’, students will write software to control all aspects of complex data transfer system, demonstrating knowledge of handshaking, transmission protocols, transmission overhead, bandwidth, memory addressing. Students will then demonstrate and analyse parallel processing of a mathematical problem using two processors. This project requires two students working as a team.
In addition to the resources found below there are supporting documents which should be used in combination with this resource. Please see:
Mini Projects - Introductory presentation.
Mini Projects - E-Log.
Mini Projects - Staff & Student Guide.
Mini Projects - Standard Grading Criteria.
Mini Projects - Reflection.
You will also need the ‘Mini Project- Dual Processor Computation’ text document.
© University of Hertfordshire 2009 This work is licensed under a Creative Commons Attribution 2.0 License .

Contents
Lecture Overview ………………………………………………………………………….3
Day 1- Communication Between Two Processors …………………………………….4
The Problem
Resources
Asynchronous Communication
Asynchronous Communication with Only Two Handshaking Signals
Definition of Master/Slave
The handshaking signals ACK and STROBE
Preparation
Day 2- Dual Processor Computation …………………………………………………..17
The Problem
Resources
Bandwidth Calculation
Unit of transfer
Asynchronous Communication with Only Two Handshaking Signals
Handshake Cycle Time
Bandwidth Measurement for this system
An example calculation
If one processor does the calculation
Two processors sharing the calculation
Time saving in first computation
Repeated Computation – see improved time saving during 1s...
Simpler notation: Normalise using tc
Normalised values for example
Method for timing each part of the calculation
Preparation
Background Reading ……………………………………………………………………42
Reflection …………………………………………………………………………………43
Remember ………………………………………………………………………………..45
Credits …………………………………………………………………………………….46

BH Dual Processor Computation Today’s Lecture
The problem
Breakdown to each day
Resources
List for each day
Preparatory work
Remind you for each day
Reflection process
Reflect on each day

Day 1 Communication between Two Processors

The Problem
To establish Master-to-Slave asynchronous data transfer between two 68000 processors, using one 8-bit port and two additional control lines only.
between two 68000 processors
Master-to-Slave
asynchronous
using one 8-bit port
two additional control only
BH Dual Processor Computation

Resources
I/O Expansion board
Coloured wires

Asynchronous Communication BH Dual Processor Computation Addr AS Data DTACK 1. AS signals valid address available on address bus – start of transfer 2. DTACK is asserted to signal that the data has been stored 4. ACK is negated to signal ready for next transfer 3. AS is negated to signal transfer complete Addr AS Data DTACK Master Slave

Asynchronous Communication with Only Two Handshaking Signals BH Dual Processor Computation Master Strobe Slave ACK I have data for you! Thanks, I’ve stored it! I might send some more Ok, I’m ready

Definition of Master/Slave
Only the Master can initiate a data transfer
The Slave can only respond

The handshaking signals ACK and STROBE
Master
Controls STROBE
Slave
Controls ACK

Preparation – Order of attack
Plan your day (Friday)
Break down the problem into steps and decide:
How to start,
what to do next…
etc…

Preparation – Resource map BH Dual Processor Computation Variable name Possible states Input or Output Allocated port pin

Preparation - Algorithms
To transmit a single byte to the Slave
To receive a single byte from the Master

Modular Structure BH Dual Processor Computation This is only an example ! main function 1 function 2 function 3 function 4 function 5 function 6

Preparation – message format
You must define a message format for data block transfer.
Define a message header which contains:
An address where the first byte will be stored in the slave’s memory (subsequent bytes will be stored contiguously)
The number of bytes in the data block (max 256)

Preparation Summary
Create Resource Map:
Define & allocate handshaking signals
Define i/o port
Write Algorithms:
To transfer a single byte from Master to Slave
Define message format

Day 2 Dual Processor Computation

The Problem
To establish the basic requirements for engaging a number of processors in solving a common problem.
A simultaneous equation with obvious parallelism will be used to develop the necessary functions in ‘C’.
A state-time diagram will be developed to summarise the efficiency of the proposed solution.

Resources
I/O Expansion board
Coloured wires

Bandwidth Calculation
This is the maximum number of bits that can be transferred in a second.
Units: Mbits/second
How much data is transferred each during one complete handshaking cycle?

Unit of transfer
In our system, how much data is transferred during one handshaking cycle?
1 byte
BH Dual Processor Computation If we continuously transmit bytes, we can measure the time taken to transfer a byte…..

Asynchronous Communication with Only Two Handshaking Signals BH Dual Processor Computation Master Strobe Slave ACK I have data for you! Thanks, I’ve stored it! I might send some more Ok, I’m ready

Handshake Cycle Time BH Dual Processor Computation Strobe ack time Unit transfer time 1 st cycle 2 nd cycle (µ s)

Bandwidth Measurement for this system
Bandwidth = 8bits/ 20 µ s
= 0.4Mbits/sec

An example calculation
Calculation of ‘z’
z = x / y
x = (a * b) / e
y = c + d

If one processor does the calculation BH Dual Processor Computation x = a*b/e y = c+d z = x/y This is how long it would take a single processor to calculate z Processor 1 time

Two processors sharing the calculation BH Dual Processor Computation Processor 1 Processor 2 x = a*b/e y = c+d z = x/y time

Two processors sharing the calculation BH Dual Processor Computation Processor 1 x = a*b/e y = c+d z = x/y time to transfer data to processor 1 time Processor 2 tc

Two processors sharing the calculation BH Dual Processor Computation Processor 1 y = c+d z = x/y time Processor 2 tc x = a*b/e

Two processors sharing a calculation BH Dual Processor Computation time x = a*b/e y = c+d z = x/y Processor 1 x = a*b/e y = c+d z = x/y Processor 2 tc time saving over single processor

Two processors sharing a calculation BH Dual Processor Computation Processor 1 x = a*b/e y = c+d z = x/y time Processor 2 tc Processor 1 x = a*b/e y = c+d z = x/y Processor 2 tc time saving over single processor Single processor x = a*b/e y = c+d z = x/y

Time saving in first computation BH Dual Processor Computation Processor 1 tx y = c+d tz time Processor 2 tc Processor 1 tx y = c+d tz Processor 2 tc Single processor ty ty time saving over single processor tx ty tz

Repeated Computation – see improved time saving during 1 st repetition of calculation BH Dual Processor Computation tx tc tx tz tc tx tc ty tx tc tz tz tz ty ty ty End of 1 st calculation tx tz Single processor ty time saving over single processor P1 P2 P1 P2

Simpler notation: Normalise using tc
To simplify the diagram, the calculation times can be described in units of tc .
To do this, just divide each time by the time for tc
eg:
if tx takes 7 times as long as tc then it will become:
tx/tc = 7

Normalised values for example
Assume, just for the sake of argument, that:
tc = 1
tx = 7
ty = 3
tz = 4

BH Dual Processor Computation Repeated Computation – see improved time saving during 1 st repetition of calculation tx tc tx tz tc tx tc ty tx tc tz tz tz ty ty ty tx tz Single processor ty P1 P2 12 12 14 8 P1 P2

Method for timing each part of the calculation
Write a probe function – just an output pin which is asserted by the processor when it starts a calculation and negated at the end.
This “probe” pin should be included in the resource map.
Calls to the probe function should be added to the code at the beginning and the end of the calculation (the probe function itself will of course increase the measured time)

BH Dual Processor Computation For this project, your level of preparation will be assessed. We will look at your logbook and the materials you have chosen to bring with you

Preparation – Resource map BH Dual Processor Computation Variable name Possible states Input or Output Allocated port pin

Preparation - Algorithms
Probe function
Review receive/transmit single byte function and handshaking

Preparation Summary
Create Resource Map:
Define & allocate handshaking signals
Define i/o port
Write Algorithm:
Probe
Review transmit/receive byte algorithms

Background Reading
From previous modules:
68000 architecture and C language programming
Useful C program template
Review related module lecture notes
A general book on ‘C’ ( bring this to the lab too!!)

Reflection Cycle BH Dual Processor Computation Reflection Observation Action

Reflection
Would you break the problem down in the same way now?
Did you spend enough time planning what you were going to do?
What did you waste time on – what could you do to reduce the amount of time spent
Do you think that you asked for too much help, or should you have asked for help sooner
With hindsight, what preparation could you have done to help you make faster progress?
Did you find the notes that you had made during preparation useful? – how could they be improved?
Do you think that you could repeat the project in six months using only your logbook record as a reference.

Remember
Be methodical:
Make progress in SMALL steps
Document as you go (comments in code and diagrams, notes in logbook)
Don’t go onto the next step until this one works FULLY and has been archived!!

This resource was created by the University of Hertfordshire and released as an open educational resource through the Open Engineering Resources project of the HE Academy Engineering Subject Centre. The Open Engineering Resources project was funded by HEFCE and part of the JISC/HE Academy UKOER programme. © University of Hertfordshire 2009 This work is licensed under a Creative Commons Attribution 2.0 License . The name of the University of Hertfordshire, UH and the UH logo are the name and registered marks of the University of Hertfordshire. To the fullest extent permitted by law the University of Hertfordshire reserves all its rights in its name and marks which may not be used except with its written permission. The JISC logo is licensed under the terms of the Creative Commons Attribution-Non-Commercial-No Derivative Works 2.0 UK: England & Wales Licence. All reproductions must comply with the terms of that licence. The HEA logo is owned by the Higher Education Academy Limited may be freely distributed and copied for educational purposes only, provided that appropriate acknowledgement is given to the Higher Education Academy as the copyright holder and original publisher.

Mini Project- Dual Processor Computation

by University of Hertfordshire, School of Electronic Communications and Electrical Engineering

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