Factors affecting CPU speed

Factors affecting CPU speed

1. № of cores

   • some computers will have multiple cores in the CPU.
     • This allows the CPU to complete multiple tasks at the same time, so long as the processes can be ran simultaneously next to each other
       • e.g. two independant programs can run on seperate cores, but not if one requires previous data, like when calculating fibonacci numbers
       • CPU cores have to communicate with each other through channels and this uses up some of the extra speed.

2. Clock Speed

   • the number of instructions a CPU can complete in a second
     • Each instruction completed is called a clock tick, the amount of ticks per second is equal to the computers clock speed
   • measured in Hertz
   • Each CPU has a fixed clock speed, however this can be altered in the computers BIOS
     • When the CPU is completing more ticks per second than suggest its being overclocked. This can cause instructions to be incomplete when the next instruction is started putting the incomplete data at risk of corruption.

3. Cache Size

   • a small amount of memory found in the CPU which stores frequently used instructions
     • the larger the cache size, the more instructions can be kept meaning less time is wasted requesting from the RAM
   • it's faster to request from Cache than it is from RAM
     • a CPU's Cache size can significantly alter how efficiently it works
   • There are multiple levels of cache, each ranging in distance from CPU. In the closest cache, the most used instructions are held whereas the furthest cache, found near your RAM, less significant instructions are stored.

4. Processor Type

   • CISC
     • complex instruction set computing
     • Used in desktops/laptops
     • Larger and requires more silicon
     • Intensive tasks will be better on a CISC CPU
     • Higher clock speed
     • use more electricity
     • require cooling
     • MANY CYCLES PER INSTRUCTION
   • RISC
     • reduced instruction set computing
     • Used in phones/tablets
     • RISC has fewer instructions than CISC
     • To do complex tasks, RISC CPUs must combine simple operations from their reduced instruction set
     • more efficient at performing simpler tasks.
     • RISC CPUs run at a lower clock speed
     • RISC CPUs are designed to use less power and they can go into 'sleep mode' when not actively processing a program.
     • more functions (including the memory and other hardware) can be combined with the CPU in one chip
     • cheaper and use less power
     • ONE CYCLE PER INSTRUCTION