The performance of the CPU is affected by the number of cores, clock speed and memory. There are different types of volatile and non-volatile memory.
Cache is a small amount of memory which is a part of the CPU - closer to the CPU than RAM. It is used to temporarily hold instructions and data that the CPU is likely to reuse.
The CPU control unit automatically checks cache for instructions before requesting data from RAM. This saves fetching the instructions and data repeatedly from RAM – a relatively slow process which might otherwise keep the CPU waiting. Transfers to and from cache take less time than transfers to and from RAM.
The more cache there is, the more data can be stored closer to the CPU.
Cache is graded as Level 1 (L1), Level 2 (L2) and Level 3 (L3):
Not a lot of physical space is allocated for cache. There is more space for RAM, which is usually larger and less expensive.
Each CPU core has its own L1 cache, but may share L2 and L3 caches.
There are two main types of CPU: CISC and RISC.
Most desktop or laptop computers use CISC (complex instruction set computing) architecture made by Intel or AMD. Smartphones and tablets use RISC (reduced instruction set computing) ARM architecture.
The key differences between the two CPUs are:
CPU expert Steve Furber explains why the ARM processor was created and why it is now used in all smartphones and tablets