Back to Memory & Storage

Primary Storage

RAM, ROM, Cache, and Virtual Memory (OCR J277 - 1.2.3)

Lesson Outcomes

By the end of this worksheet, you should be able to:

  • Define RAMRandom Access Memory: Volatile memory that stores currently running programs and data., ROMRead-Only Memory: Non-volatile memory containing essential startup instructions (BIOS/firmware)., and CacheVery fast, small memory located on or near the CPU, storing frequently accessed data/instructions. memory.
  • Explain the difference between volatileData is lost when the power is turned off. and non-volatileData is retained even when the power is turned off. memory.
  • Describe the purpose of ROM in the computer's startup sequence.
  • Explain the need for Virtual MemoryUsing secondary storage (like HDD/SSD) as if it were RAM when physical RAM is full. and identify its main drawback.
  • Compare the main types of primary storage in terms of speed, capacity, volatility, and typical use.

Starter Task

Quick check! Let's recall some key concepts about memory and storage.

1. True or False: RAM is non-volatile (it keeps data without power).

2. RAM is an example of which type of storage?

3. Which type of storage is generally faster for the CPU to access directly?

4. In one sentence, why is ROM essential for a computer to start up?

ROM is non-volatile and holds the essential startup instructions (like the BIOS/bootloader) needed to load the operating system when the computer is first turned on.

Task 1: Quick Check - True or False? (Max 5 points)

Test your basic knowledge about memory types. Hover over keywordsKeywords like RAM, ROM, Volatile etc. will have dotted underlines. Hover over them for definitions if you need a reminder! if you need a hint.

1. RAMRandom Access Memory: Volatile memory that stores currently running programs and data. is typically faster to access than secondary storage like an HDD.

2. Data stored in ROMRead-Only Memory: Non-volatile memory containing essential startup instructions (BIOS/firmware). can be easily changed by the user.

3. CacheVery fast, small memory located on or near the CPU, storing frequently accessed data/instructions. memory is faster but smaller than RAM.

4. Virtual MemoryUsing secondary storage (like HDD/SSD) as if it were RAM when physical RAM is full. uses part of the secondary storage.

5. Turning off the computer erases the data stored in ROM.

Task 2: Comparing Memory Types (Max 6 points)

For each characteristic, choose the memory type that BEST fits the description.

1. Stores the operating system, running applications, and current user data.

2. Non-volatileData is retained even when the power is turned off. memory containing the computer's startup instructions (BIOS/firmware).

3. Small amount of very fast memory located on or near the CPU.

4. Used when RAM is full; much slower than RAM.

5. VolatileData is lost when the power is turned off. memory, meaning its contents are lost when power is off.

6. Stores frequently accessed instructions and data to speed up CPU processing.

Task 3: Memory Analogies (Max 4 points)

Drag the memory type from the pool to match the best analogy describing its function.

Analogy

Your desk where you keep things you're currently working on.
An instruction manual built into an appliance that tells it how to start.
A small pocket where you keep the few tools you use most often.
Moving less-used items from your desk to a nearby filing cabinet when the desk gets full.

Memory Type Pool

RAM
ROM
Cache
Virtual Memory

Task 4: Boot Sequence Simulation

Click the button to simulate the basic steps involved when a computer starts up, highlighting the role of ROM and RAM.

  • Power button pressed.
  • CPU loads initial instructions from ROM (BIOS/UEFI).
  • BIOS/UEFI performs Power-On Self-Test (POST) to check hardware.
  • BIOS/UEFI locates the boot device (e.g., SSD/HDD).
  • Bootloader program is loaded from the boot device into RAM.
  • Bootloader loads the main Operating System kernel into RAM.
  • Operating System takes control and loads user interface/drivers.

Task 5: Virtual Memory Simulation (Max 1 point)

Simulate loading programs and see how virtual memory is used when RAM fills up. Pages moved to the disk (virtual memory) are shown in yellow.

RAM (4 Pages)

Disk (Virtual Memory)

Status: Ready

What is the main drawback of using virtual memory?

Key Takeaways

  • RAM (Random Access Memory): VolatileData is lost when the power is turned off. memory storing currently running OS, applications, and data. Relatively fast access.
  • ROM (Read-Only Memory): Non-volatileData is retained even when the power is turned off. memory holding essential startup instructions (BIOS/firmware). Cannot be easily changed.
  • Cache Memory: Small, extremely fast volatileData is lost when the power is turned off. memory on/near the CPU. Stores frequently used data/instructions to reduce access time to RAM.
  • Virtual Memory: A technique using secondary storage (HDD/SSD) as an extension of RAM when physical RAM is full. Allows more applications to run but is much slower due to disk access (swappingThe process of moving data between RAM and secondary storage (virtual memory). / pagingThe process of managing memory by dividing it into fixed-size blocks called pages.).
  • Volatility: Determines if memory retains data without power (Non-volatile) or loses it (Volatile).
  • Performance Hierarchy: Speed: Cache > RAM > Virtual Memory. Capacity: Virtual Memory (Disk) > RAM > Cache.

Task 6: Exam Practice Questions

Apply your knowledge to these exam-style questions.

1. Explain the difference between RAM and ROM. [4 marks]

2. Describe the purpose of cache memory. [2 marks]

3. Explain why virtual memory might be needed and one drawback of using it. [3 marks]

Task 7: Worksheet Progress

Check your score based on the interactive quiz questions and activities.

Your Score: 0 / 0

Note: Score based on Tasks 1, 2, 3, and 5 (Quiz Q only). Starter Task, Boot Sim & Exam practice are not auto-scored.

What's Next?

Now you understand the different types of primary storage!

In the next lesson, we'll explore Secondary Storage, looking at:

  • The need for permanent storage (Hard Disk Drives, Solid State Drives, Optical Discs).
  • How these different storage technologies work and their characteristics (capacity, speed, durability, cost etc.).

Extension 1: Cache Levels (L1, L2, L3)

Match the cache level to its typical characteristics by dragging the cache type.

Characteristics

Fastest speed, smallest size, often per CPU core.
Medium speed & size, buffer between L1 & L3/RAM.
Slowest cache speed, largest size, shared by cores.

Cache Type Pool

L1 Cache
L2 Cache
L3 Cache

Research Task: Find out the typical L1, L2, and L3 cache sizes (in KB or MB) for a recent CPU model (e.g., Intel Core i7 or AMD Ryzen 7).

Extension 2: Modern RAM (DDR Generations)

Test your knowledge about DDR RAM generations.

1. What does DDR stand for in DDR RAM?

2. Compared to DDR3, DDR4 RAM generally offers:

3. Can you install DDR5 RAM into a motherboard designed only for DDR4?

Research Task: Besides speed (MHz/MT/s), what do RAM timings (like CL16, CL32) refer to, and how do they affect performance?