Processor Architecture and Performance
Explaining stored-program operation, processor components, registers, instruction execution and factors that affect system performance.
How to study A-level Computer Science
Define the problem and representation, trace the state change, justify the algorithm or architecture, then test the result against requirements, evidence and constraints.
Core concepts
Concept 1
A stored-program processor fetches, decodes and executes instructions while data and instructions share addressable storage.
Exam cue: Trace the relevant registers and buses through fetch, decode and execute.
Concept 2
The control unit, arithmetic logic unit, registers, buses and clock coordinate instruction processing.
Exam cue: Distinguish an address, an instruction and the data stored at an address.
Concept 3
Clock rate, cores, cache, architecture and workload interact, so no single measure determines performance.
Exam cue: Evaluate performance claims for a stated workload and bottleneck.
Risk pitfalls and guardrails
Saying the program counter stores the current instruction.
Guardrail: Do not substitute a memorised definition or generic advantage until you have identified the input, state, stakeholder and constraint in the task.
Assuming doubling clock rate always doubles application performance.
Guardrail: Do not substitute a memorised definition or generic advantage until you have identified the input, state, stakeholder and constraint in the task.
Confusing cache with long-term secondary storage.
Guardrail: Do not substitute a memorised definition or generic advantage until you have identified the input, state, stakeholder and constraint in the task.
Memory anchors
Program Counter
The program counter holds the address of the next instruction to fetch.
Memory Address Register
The MAR holds the address currently being accessed.
Memory Data Register
The MDR holds data or an instruction being transferred to or from memory.
Current Instruction Register
The CIR holds the instruction being decoded or executed.
Cache
Cache keeps frequently or recently used data close to the processor.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What is the role of the program counter?
What is the role of the memory address register?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
What is Pass Harbor?
Completely free exam prep for 247 UK exams.
- Practice questions
- Flashcards
- Study guides
- Mock exams
- No registration
- No paywall
- Start instantly
“No more expensive exam prep. Quality study tools should be accessible to everyone.”