# OCR GCSE Computer Science: CPU System Architecture Guide
> Learn about CPU architecture, Von Neumann architecture, the Fetch-Decode-Execute cycle, and embedded systems for OCR GCSE Computer Science.

Tags: gcse-computer-science, cpu-architecture, von-neumann, embedded-systems, revision-guide, fetch-decode-execute, ocr, computer-science-notes
## OCR GCSE Computer Science: System Architecture
* Revision guide covering CPU Architecture, Memory, and Embedded Systems.

## The Central Processing Unit (CPU)
* Purpose: To process data and execute instructions.
* Acts as the 'brain' of the computer.
* Core cycle: Fetch, Decode, Execute.

## Von Neumann Architecture
* Defined by the 'Stored Program Concept'.
* Instructions and data are stored together in the same memory (RAM).
* Uses a single control unit and one set of buses.

## Key CPU Components
* **ALU (Arithmetic Logic Unit):** Performs calculations and logical decisions.
* **CU (Control Unit):** Coordinates CPU activity and decodes instructions.
* **Cache Memory:** Fast, small memory on the CPU for frequently used data.

## CPU Registers
* **PC (Program Counter):** Holds the address of the next instruction.
* **MAR (Memory Address Register):** Holds the memory address for data fetch/store.
* **MDR (Memory Data Register):** Holds the actual data/instruction fetched.
* **ACC (Accumulator):** Stores results from the ALU.

## The Fetch-Decode-Execute Cycle
1. **Fetch:** Address copied from PC to MAR; instruction fetched to MDR; PC increments.
2. **Decode:** CU interprets the instruction in the MDR.
3. **Execute:** The operation is performed (e.g., calculation or data move).

## Factors Affecting CPU Performance
* **Clock Speed:** Number of cycles per second (GHz).
* **Cache Size:** More cache reduces reliance on slower RAM.
* **Number of Cores:** Enables processing multiple instructions simultaneously.

## Embedded Systems
* Built into larger devices with a dedicated function (e.g., washing machines, vehicles).
* Characteristics: low power, real-time operation, often runs on firmware (ROM).
* Comparison: Unlike general-purpose PCs, they are cheaper and specialized for one task.

## Practice & Exam Technique
* Includes model answers for 6-mark questions describing how CPU and RAM interact.
* Focuses on the roles of the CU, cache memory, and the importance of each F-D-E stage.
---
This presentation was created with [Bobr AI](https://bobr.ai) — an AI presentation generator.