Study guide: CPU Performance Factors

📋 Course Outline

1. Clock Speed
2. CPU Cores
3. Cache Memory
4. Parallel Processing
5. Threading Models
6. Combined Performance and Bottlenecks

📖 1. Clock Speed

🔑 Key Concepts & Definitions

• Clock speed: the frequency at which the CPU operates

★ Must-know

📌 A higher clock speed generally allows a CPU to process more instructions per second and complete instructions faster when otherwise identical CPUs are compared.

Further detail

📌 Increasing clock speed also increases power consumption and heat production.

• Clock speed is measured in Hertz (Hz), and 1 Hz equals 1 clock cycle per second.

💡 Memory Hook

Higher frequency → more instructions per second → faster processing, but also more heat and power use.

📖 2. CPU Cores

🔑 Key Concepts & Definitions

• CPU core: an independent processing unit within a CPU

★ Must-know

📌 More cores improve performance when software is designed to use them through parallel processing or multithreading.

Further detail

• Dual-core, quad-core, hexa-core, and deca-core CPUs contain 2, 4, 6, and 10 cores respectively, while CPUs can also contain 12, 16, 24, or 64 cores.

• Each CPU core can perform its own fetch-decode-execute cycle.

💡 Memory Hook

D-Q-H-D: dual, quad, hexa, deca-core.

📖 3. Cache Memory

🔑 Key Concepts & Definitions

• Cache: small, very fast memory located in or near the CPU that stores frequently accessed instructions and data

📝 Essential Points

• The cache levels are:
  • L1: smallest and fastest
  • L2: larger but slower than L1
  • L3: larger and slower than L1 and L2, faster than RAM, and shared between cores

📌 A larger cache reduces the need to fetch information from slower main memory (RAM), reducing average memory access time and CPU waiting time.

💡 Memory Hook

L1 → L2 → L3: increasing size and decreasing speed.

📖 4. Parallel Processing

🔑 Key Concepts & Definitions

• Parallel processing: the processing of multiple instructions or tasks at the same time

★ Must-know

📌 Parallel processing can significantly improve performance in software designed to use multiple cores.

Further detail

• Parallel processing is particularly useful for multitasking and workloads that can be divided into separate tasks, such as processing different parts of a video-rendering task simultaneously.

💡 Memory Hook

Different CPU cores simultaneously handling separate pieces of a video-rendering task.

📖 5. Threading Models

🔑 Key Concepts & Definitions

• Threading: how a processor handles and executes multiple sequences of instructions called threads
• Single threading: allows a CPU or core to execute one thread at a time
• Multilevel threading: allows a single CPU core to manage more than one thread at a time

📝 Essential Points

📌 Multilevel threading can improve performance in multitasking and parallel processing.

💡 Memory Hook

Single threading handles one thread at a time, whereas multilevel threading handles more than one thread at a time.

📖 6. Combined Performance and Bottlenecks

🔑 Key Concepts & Definitions

• Bottleneck: when one CPU characteristic limits the performance of the rest of the CPU

★ Must-know

• The combined CPU performance factors are:
  • clock speed
  • number of cores
  • cache size
  • parallel processing
  • threading

Further detail

• A CPU with high clock speed, many cores, and a small cache may access RAM more frequently, causing the CPU to wait for data and reducing overall performance.

💡 Memory Hook

A weak characteristic, such as a small cache, can limit otherwise strong CPU characteristics.

📊 Synthesis Tables

Cache Levels