mini project- dual processor computation

Mini Project – Dual Processor ComputationAuthor: University of HertfordshireDate created:Date revised: 2009

AbstractThe 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.

http://www.herts.ac.uk/courses/BEng-DSCE.cfm

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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


Resources

• I/O Expansion board

• Coloured wires


Asynchronous Communication

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

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

• MasterControls 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

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

main

function 1 function 2 function 3

function 4

function 5

function 6

This is only an example !


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

If we continuously transmit bytes, we can measure the time taken to transfer a byte…..


Asynchronous Communication with Only Two Handshaking Signals

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

Strobe

ack

time

Unit transfer time

1st cycle 2nd cycle

(µs)


Bandwidth Measurement for this system

Bandwidth = 8bits/ 20µs

= 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

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

Processor 1

Processor 2


time



Processor 1 x = a*b/e

y = c+d

z = x/y

time to transfer data to processor 1

time

Processor 2

tc



Processor 1

y = c+d

z = x/y

time

Processor 2

tcx = a*b/e


Two processors sharing a calculation

time



y = c+d

z = x/y

Processor 2

tc

time saving over single processor


Two processors sharing a calculation


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


Single processor



Time saving in first 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


tx ty tz


Repeated Computation – see improved time saving during 1st repetition of calculation

tx tc

tx

tztc

tx

tc

ty

tx tc

tz

tz tz

ty

ty ty

End of 1st calculation

tx tzSingle processor

ty


P1P2

P1P2


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


Repeated Computation – see improved time saving during 1st repetition of calculation

tx tc

tx

tztc

tx

tc

ty

tx tc

tz

tz tz

ty

ty ty

tx tzSingle processor

ty

P1P2

12

12

14

8

P1P2


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)


For this project, your level of preparationwill be assessed.

We will look at your logbook and the materials you have chosen to bring with you


Preparation – Resource map

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

Reflection

ObservationAction


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.

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