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OCR H446 1.1.3 RAM and ROM roles and performance

Part 3 of 6 · H446 1.1.3 · Input, output and storage

OCR H446 1.1.3: RAM and ROM roles and performance. Students learn to track RAM and ROM through power and use states, apply ROM to start-up firmware, fixed programs and compact system software, and explain additional RAM through reduced virtual-memory reliance.

Students will:

  • track RAM and ROM through power and use states
  • explain memory roles across different systems
  • explain when additional RAM reduces reliance on virtual memory

Inside: 5 explanation cells, 1 multiple-choice question, 2 fill-in-the-blanks cells and 4 written answers. 38 marks, about 55 to 70 minutes.

Series: H446 1.1.3 · Input, output and storage, part 3 of 6.

Shared by Coding PathwayVerified teacher

  • 12 cells
  • About 60 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 3 Sept 2026

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The whole resource, exactly as a class sees it. Answers and marking are held back.

RAM and ROM roles and performance

RAM and ROM are primary-memory technologies with different roles. A complete answer states what each memory holds, whether the contents normally change during use, what happens without power and why those characteristics matter in the system.

Follow power and use states

RAM and ROM through power-on, active use and power-off follow the state, not just the acronym ROMnon-volatilepersistent instructions/settingsnot normally changed in use RAMvolatileactive instructions and dataread and written during use power onpersistent code/settings availableactive useworking instructions/data held in RAMpower offRAM state lost; ROM content remains More RAM can keep more active data away from slower virtual memory,reducing swapping and the risk of thrashing.

RAM is volatile, directly accessible working memory holding active instructions and data. ROM is non-volatile and normally retains instructions or settings that should remain available and not be routinely overwritten. Real implementations vary, so focus on the role given in the question and explain why it is useful in that system.

Why systems need ROM

ROM provides non-volatile memory for instructions or settings that must still be available when a device is switched on again.

  • A desktop or laptop can retain start-up firmware, such as the BIOS or UEFI firmware. This begins the start-up process; the main operating system is normally loaded from secondary storage into RAM.
  • An embedded system can retain its control program, device firmware, calibration values or fixed configuration. These remain available after power loss and are protected from routine alteration.
  • A small dedicated device can retain most or all of a compact operating system or application as firmware when the software changes rarely and must be available immediately.

The useful explanation is not simply “ROM is non-volatile”. State what is stored, why it must persist and how that helps the particular system.

Worked explanation: why more RAM can improve performance

Suppose a workstation repeatedly switches between an editor, a simulation and a large dataset. With too little RAM, some active pages/data must be moved between RAM and virtual memory on secondary storage. Secondary storage is slower to access and the movement itself takes time. More RAM can keep more active material in primary memory, reducing swapping and the risk of repeated paging/thrashing.

Complete explanation: more active data in RAM → less reliance on virtual memory and swapping → more accesses use faster RAM and less movement occurs → improved performance for this workload. “RAM is fast” alone does not explain how performance changes.

Multiple choice1 mark

Which statement best explains a ROM use in a sealed environmental controller?

  • AIt holds every live sensor reading because it is faster than all RAM
  • BIt extends RAM by swapping active pages
  • CIt retains firmware/configuration needed after power loss and not normally changed during use
  • DIt is remote storage presented as a local folder
Fill in the blanks4 marks
RAM is gap 1 and holds gap 2 instructions/data. ROM is gap 3 and retains persistent instructions/settings. Additional RAM may reduce use of slower gap 4 memory.
  • volatile
  • active
  • non-volatile
  • virtual
  • cache
Written answer6 marks

A student says, ‘Adding RAM makes the CPU clock run faster.’ Correct the claim and explain how adding RAM may improve performance when many large applications are active. Include virtual memory and swapping/thrashing.

Do not claim improvement is guaranteed when RAM was not the bottleneck.

Students type their answer here.

Written answer4 marks

A portable audio guide already uses ROM for start-up code. Describe a different use of ROM in this system, such as storing its control program, fixed interface resources, configuration or a compact dedicated operating system. Explain why ROM is suitable for your chosen use.

Identify the content first, then connect persistence or protection from routine alteration to a useful consequence for the audio guide.

Students type their answer here.

Apply the state model across systems

Transfer the RAM, ROM and additional-memory reasoning to desktop, mobile and embedded systems with different active and persistent data needs.

Written answer9 marks

Apply the RAM and ROM roles to each system below. For every system, state one important RAM role, state one important ROM role or explain why a proposed ROM role would be unsuitable, and explain why the difference between active and persistent content matters.

  1. A desktop video editor.
  2. A battery-powered sensor node.
  3. A games console.

Use the same memory principles in different contexts; do not rely on device stereotypes. Each system is worth 3 marks.

Students type their answer here.

Written answer10 marks

Create a five-row comparison for RAM, ROM, cache, secondary storage and virtual memory. For each term, state its main purpose and one relevant difference in location, volatility, speed or data movement. Use the comparison to explain why calling all five simply ‘memory’ would not answer a question about performance or persistence.

Keep cache detail at 1.1.1 level and virtual-memory management at introductory 1.2.1 level. Each term is worth 2 marks.

Students type their answer here.

Fill in the blanks4 marks
RAM holds checkpoint gap 1 instructions/data and is checkpoint gap 2. ROM retains persistent content and is checkpoint gap 3. More RAM can reduce swapping to slower checkpoint gap 4 memory.

Consolidate your understanding

Check that each memory explanation states what is held, whether it persists and why that characteristic matters in the supplied system.