Tech Level 3 Cyber security AO2b, 2c.

Learning Objectives Learners must be able to: identify the steps of the fetch-execute cycle describe the purpose of each step and the overall purpose of the cycle explain the term ‘interrupt’ for computers explain purpose an interrupt in an fetch-execute cycle explain the effect of an interrupt on the fetch-execute cycle capture the fetch-execute cycle with and without the interrupt, in diagrammatic form compare and contrast IRQ and NMI.

Assessment Outcomes 2B – The steps of the Fetch-Execute cycle 2C – The effect and purpose of an interrupt on the Fetch-Execute cycle 2D – Maskable Interrupts (IRQ) and Non-Maskable Interrupts (NMI)

Summer Project Recap What are the main components of the CPU? What do they do? What is a multi core CPU? What is a core? When would you use a single core CPU? When would you use a multi core CPU? What are the benefits of a multi core CPU? What negatives may a multi core CPU present?

The Fetch Execute Cycle: Pre-Reading Your notes should refer to the assessment outcomes listed on the right hand side. This week pre-reading will be completed in class, usually it will be in your directed time. Resources: Chapter 6 – CompTIA A+ Certification All- In-One Exam Guide Chapter 25-Chapter 26 AQA AS and A Level Computer Science (Heathcote and Heathcote) 2B – The steps of the Fetch-Execute cycle 2C – The effect and purpose of an interrupt on the Fetch-Execute cycle

Interrupt handling Candidates should be able to explain how interrupts are used to obtain processor time and how processing of interrupted jobs may later be resumed, (typical sources of interrupts should be identified and any algorithms and data structures should be described)

Interrupt handling Create a PowerPoint presentation describing what an interrupt is, the different types of interrupt and how the interrupts work Use the presentation in the shared area to help you find the information you need

Interrupt Introduction The simplest way of following instructions is shown below: What if something went wrong? Would this set of instructions still work?

Interrupts An interrupt is messages sent to the processor which stops a job due to a certain circumstance i.e. hardware failure or I/O issues The diagram on the slide previously needs to be modified to take this into account

Interrupt flowchart The problem with this diagram is that the original program will not finish if there are multiple interrupts. So how can we get round this?

Interrupt modified flowchart The interrupts are held in a queue. Each interrupt is given a priority which determines where it is in the queue. The more important the job, the higher the priority for it to be resumed first.

Graded exercises Open the graded exercises from computing.smestow.org You should complete the Grade D challenges using your pre-reading notes to help you. You should then attempt your target grade challenge

Crib Sheets A crib sheet is a document with condensed notes and key facts that you will need to remember. It helps you consolidate your knowledge into easy to remember facts. You will create a Crib Sheet for each assessment outcome studied this year. It is worth having a separate notepad / book for crib sheets. You should complete no more than half a page (a5) per Assessment Outcome – this has to include all key facts and information including diagrams.

Assessment outcome review 2B – The steps of the Fetch-Execute cycle 2C – The effect and purpose of an interrupt on the Fetch-Execute cycle 2D – Maskable Interrupts (IRQ) and Non-Maskable Interrupts (NMI) Create a revision crib sheet with key facts for the above assessment outcomes.

Pre-Reading for next week Make notes on: The concept of parallel processing and pipelines in computers The purpose of pipelines in computers Registers in computers: CPU Registers Special Registers The accumulator The reasons for cooling computers Different methods of cooling computers Resources: See Lesson 3 folder.