--- title: "Choose the hardware" subtitle: "Inside a computer · Specs and speed · Lesson 3" --- # Choose the hardware **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** Two computers cost about the same. One has twice the cores, the other four times the RAM. Which is better? :::teacher-note **In one sentence:** Students compare two computers on different jobs, follow four steps to a justified choice, and build the cheapest computer that meets a media-lab brief within a budget (AC9TDI8K01 node 3). **Students should be able to say:** I can choose hardware for a job and justify it with specs. I can explain a trade-off between two specs (more RAM or a faster processor). I can stay within a budget by spending on the bottleneck. **Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Predict :::keep-together **For exporting video, Option A has 8 cores and 8 GB of RAM; Option B has 4 cores and 32 GB of RAM. Both cost about $700. Which exports faster?** ☐ Neither can export video ☐ The same: they cost the same ☐ Option A: the export uses all 8 cores ☐ Option B: it has four times the RAM My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** Option A: 61 seconds against B's 103. The export needs processor power most; A swaps a little, but its cores matter more. ::: ## Run Try it on the board in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Worked example: four steps to a choice :::keep-together ### Video editing, step by step 1. $\text{1. What does the job need?}$ — The export uses up to 8 cores and needs 16 GB of RAM. 2. $\text{2. Compare on that}$ — A: 50 s processor + 8 s swapping + 3 s = 61 s. B: 100 s + 3 s = 103 s. 3. $\text{3. Weigh the trade-offs}$ — A is short of RAM (it swaps); B has RAM it can't use but half the cores. 4. $\text{4. Justify}$ — Choose A: the processor is the export's bottleneck. Add RAM to 16 GB if the budget allows: 53 s. Now work out A with 16 GB. **Option A with its RAM raised from 8 GB to 16 GB (costs $60 more). How many seconds is the export now?** Answer: {{field-15}} ::: :::teacher-note **Answer:** 53 Processor 1200 ÷ (8 × 3) = 50 s, storage 3 s, no swapping: 53 s, for $780. ::: :::keep-together ### Find the mistake **Sam chooses a computer for video editing. Click the line where it first goes wrong.** ``` 1 Option B has 32 GB of RAM; Option A has 8 GB. 2 32 is the bigger number. 3 So Option B is better for every job. 4 Sam buys Option B for video editing. ``` Line: {{field-15}} Why is it wrong? {{lines-2}} ::: :::teacher-note **Answer:** line 3 Line 3: a bigger number only helps if that part is the job's bottleneck. For exporting video it is the processor, so A is the better choice. ::: :::keep-together ### A different job **Same two options, but the job is keeping 30 browser tabs open. Which is better?** ☐ The same ☐ Option B: tabs need RAM, and A has to swap ☐ Option A: more cores ☐ Neither ::: :::teacher-note **Answer:** Option B: tabs need RAM, and A has to swap B: 2 s against A's 6 s. A different job, a different best choice. ::: :::typical ## Vary: change the job **Tabs.** **Game.** **Download.** Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} ::: ## Choose for the job :::keep-together ### A school laptop **A Year 8 student's laptop: web browsing, documents and video calls. Where should the money go?** ☐ A graphics card ☐ 4 TB of storage ☐ A 32-core processor ☐ Enough RAM (about 8–16 GB), an SSD and good Wi-Fi ::: :::teacher-note **Answer:** Enough RAM (about 8–16 GB), an SSD and good Wi-Fi Tabs need RAM, starting and opening need an SSD, calls need the network. ::: :::keep-together ### AI **A computer for training AI models. Which one part matters most?** ☐ A bigger screen ☐ A graphics card ☐ A big hard disk ☐ A faster network ::: :::teacher-note **Answer:** A graphics card Training is millions of small sums: a graphics card does thousands at once. ::: :::keep-together ### A file server **A school file server where 1,000 students save and open work. Which pair matters most?** ☐ The fastest single core ☐ Lots of storage and a fast network ☐ A graphics card and a big screen ☐ The smallest, cheapest parts ::: :::teacher-note **Answer:** Lots of storage and a fast network Everyone's files have to fit, and many people send and fetch them at the same time. ::: :::keep-together ### Review: bottlenecks **Review: a laptop with a hard disk takes 2 minutes to start up. What is the bottleneck?** ☐ Network ☐ Graphics ☐ Storage size ☐ Storage speed ::: :::teacher-note **Answer:** Storage speed Starting up reads programs from storage: an SSD fixes it. ::: ## Make: the media lab **Build it.** **Justify it.** Then: write one sentence a parent could read: which computer, and why. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} ## Exit ticket :::keep-together **Two laptops cost the same. One has more RAM, the other a faster processor. Which would you choose for a student who keeps many tabs open, and why?** {{lines-3}} ::: :::teacher-note **Answer:** The one with more RAM: many tabs need working space, and too little RAM swaps to storage. The faster processor wouldn't fix that. :::