This key facts covers Quick Reference - Virtual Memory within Virtual Memory for GCSE Computer Science. Revise Virtual Memory in 3.4 Computer Systems for GCSE Computer Science with 15 exam-style questions and 16 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 9 of 10 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Quick Reference - Virtual Memory
Core Concept:
- Virtual memory = using hard drive as RAM extension
- Activated when physical RAM is full
- Data swapped between RAM ↔ hard drive (paging)
- Transparent to user (OS handles automatically)
Three Main Benefits:
- Run more programs than physical RAM allows
- Prevents out-of-memory crashes
- Enables larger programs to run
Three Main Drawbacks:
- Much slower than physical RAM (100-1000x slower)
- Disk thrashing when overused (system becomes unusable)
- Increased wear on SSDs from constant writing
Speed Comparison:
- RAM access: 10-100 nanoseconds (0.00001 ms)
- SSD access: 0.1 milliseconds (1000x slower than RAM)
- HDD access: 10+ milliseconds (100,000x slower than RAM)
The Golden Rule:
Virtual memory is a BACKUP, not a replacement for physical RAM. If you're constantly using virtual memory, you need more RAM!
Practice questions for Virtual Memory
What is virtual memory?
Explain how virtual memory works when a user opens more programs than RAM can hold.