Year 10 Computer Science Hardware - CPU and RAM

Learning Objectives Understand the function of primary memory (RAM) Understand how RAM interacts with the CPU and secondary storage

Key Questions What is RAM? How is RAM different to secondary storage devices (e.g. hard drives) Why can’t all data be stored in RAM? How does RAM affect the performance of a computer system?

RAM - The Basics RAM is short for Random Access Memory If you have ever bought a desktop computer, you will have seen the main/primary memory referred to as random-access-memory (RAM). But what is RAM and why do we need it?

RAM - Function RAM is used to temporarily store data that the CPU will use for data and instructions (programs). RAM is very fast - much faster than a hard drive or solid state drive. Computer processors (CPU’s) are also really, really fast. Hard drives are very slow in comparison. If computers handled and processed data by writing and reading directly from the hard drive, computers would be extremely slow too, because the hard drive couldn't keep up with the processor's speed. RAM is there to address this problem. It's a place where data is temporarily stored that is really really fast to read and write from.

Hard Drive, CPU and RAM - A Journey You decide that you would like to open Microsoft Word on your computer: RAM CPU Hard Drive / SSD The CPU fetches the program data and carries out/processes any instructions (e.g. displaying typed text to a screen) Program data (e.g. Microsoft Word) is transferred from the hard drive to the RAM. Microsoft Word A program is a series of instructions to the CPU. Before an instruction can be executed, program instructions and data must be placed into memory from an input device or a secondary storage device (the process is further complicated by the fact that, as we noted earlier, the data will probably make a temporary stop in a register).

Hard Drive, CPU and RAM RAM Hard Drive / SSD New files that are created, or changes made to files while the computer system is in use, need to be saved before the computer is switched off. This is done by copying the live data from RAM to the secondary storage. RAM The user closes Microsoft Word. Program data is removed from RAM. Document is transferred to the Hard Drive Hard Drive / SSD Microsoft Word

Key Points RAM is described as volatile, which means that its content is lost when the power is turned off. This means that computers also need non-volatile memory to store any programs that must run when the computer is first turned on. The Windows Operating System, for example, needs to be transferred into RAM during startup.

Task 1 - Questions 1) What is the purpose of RAM in a computer system? 2) Is RAM volatile or non volatile memory? Justify your answer Ram is ……. Memory. This is because… 3) Explain why a computer system needs both primary memory (RAM) and secondary memory (hard drive/solid state drive). 4) Give one example of data that may be stored in RAM. 1 - RAM temporarily stores all the data of programs and applications currently open on the computer. This enables the CPU to fetch data and carry out any instructions. 3 - A computer system needs RAM to temporarily store the data for live programs, whilst it needs long term storage to store the data of files you would need to access in future

Task 2 - Task Manager Windows allows us to see the programs that are currently being stored in RAM, by using the Task Manager. Access the task manager by pressing Ctrl-Shift and Exit on your keyboard. Answer the following questions in your books: How much primary memory (RAM) space do the school computers have? Close all applications. What is the current memory usage in %? Open 5 Google Chrome tabs, Microsoft Word, Adobe Photoshop and Dreamweaver. Explain the impact this have on the memory usage?

Task 3 - Extension - Research Task What happens when you have so many programs open you no longer have any space left in RAM to temporarily store them? Consider: The impact this may have on the performance of the PC Any potential solutions to this issue.

Virtual Memory Virtual memory. What happens if you’ve got so many programs open that the RAM becomes filled up with programs (instructions) and data? Does the computer stop working? No, a typical modern computer system has another option up its sleeve… Virtual memory. Virtual memory is actually hard-drive (hard-disk) space which acts as RAM (although it operates a lot more slowly than RAM)

Task 4 - How RAM affects performance of a computer system So as we’ve just seen, RAM is needed to supply to the CPU with data and instructions from programs currently in use. Smaller amount of RAM – limited multi tasking and greater need to use slower virtual memory Larger amount of RAM – greater storage of programs / data leading to faster performance and effective multi-tasking.