Clock Speed
Definition
The number of cycles the CPU can perform per second, measured in Hertz (Hz). Modern CPUs are measured in GHz (billions of cycles per second).
Example
A 3.5 GHz processor can perform 3.5 billion cycles per second.
| Advantage | Disadvantage |
|---|---|
| More instructions executed per second | Generates more heat |
| Faster program execution | Higher power consumption |
| Diminishing returns at very high speeds |
Number of Cores
Definition
A CPU containing multiple independent processing units (cores), each capable of executing instructions independently.
| Advantage | Disadvantage |
|---|---|
| Parallel processing - multiple tasks simultaneously | Software must be written to utilise multiple cores |
| Better multitasking performance | Not all tasks can be parallelised |
| More efficient than increasing clock speed | Increased complexity and cost |
Key Point
Doubling the cores does NOT double performance. Performance gain depends on how well software can split tasks across cores.
Cache Memory
Definition
Small, extremely fast volatile memory located on or near the CPU that stores frequently accessed data and instructions.
| Level | Size | Speed | Location |
|---|---|---|---|
| L1 | Smallest (32-64KB) | Fastest | On CPU core |
| L2 | Medium (256KB-1MB) | Fast | On CPU (per core or shared) |
| L3 | Largest (2-32MB) | Slower than L1/L2 | Shared between all cores |
Key Point
Cache reduces the time spent waiting for data from RAM. A cache hit (data found in cache) is much faster than a cache miss (data must be fetched from RAM).