What is a central processing unit (CPU)?

The CPU executes program instructions and performs general-purpose computation, including arithmetic, comparisons and moving data. It is important but does not determine total performance alone: RAM, storage, graphics hardware and software also influence results.

How do instructions, cores and caches work?

A processor fetches instructions, decodes them and executes the required operations. Modern designs may overlap stages and work on multiple instructions. A core contains processing resources, and multiple cores can run suitable work in parallel. Execution-thread counts are not the same as physical-core counts. Caches keep frequently needed information near the processor, reducing access to slower memory. RAM capacity and cache capacity therefore serve different purposes. Tasks with dependent steps cannot necessarily gain proportional speed from additional cores.

Why is clock speed alone insufficient?

Clock frequency concerns cycles per second, whereas work completed per cycle depends on architecture and the program. Comparing different designs solely by GHz can therefore mislead. Power limits and cooling affect sustained workloads, and a brief peak speed can differ from long-running performance. Office tasks, compilation and image processing benefit from different characteristics. Investigating a slowdown requires considering processor activity alongside memory pressure, storage waits and measurements from the application itself.