Types of Processor

Types of Processor

1. Instruction Sets

   • All CPU's have a group of commands called an instruction set, this is used to carry out different tasks.
     • These instruction sets are written in 'Machine Code.'
   • There are two main types of instruction set.
     • CISC
       • Complex Instruction Set Computing
         • Used in laptops and desktop computers, made by Intel or AMD.
         • Has more complex hardware
         • Multiple machine cycles per instruction
         • Physically larger in size and require more silicon to make, this makes it more expensive.
         • Greater energy consumption
         • Will work better with more intensive tasks
         • Can't support pipelining
     • RISC
       • Reduced Instruction Set Computing
         • Used in smartphones and tablets, based around ARM processor.
         • Has simpler hardware
         • Single machine cycle per instruction
         • Smaller in size as less complex circuitry required, less silicon needed to make, this makes it cheaper.
         • Lower energy requirements, and can go into "sleep mode" when not actively processing.
         • Run at a lower clock speed, but can perform simpler tasks more quickly and efficiently than the CISC.
         • Can support pipelining

2. Parallel Processing

   • This is where a computer carries out multiple computations simultaneously to solve a given problem.
     • MISD - Multiple Instruction Single Data
     • SIMD - Single Instruction Multiple Data
     • MIMD - Multiple Instruction Multiple Data
   • Advantages
     • More jobs can be done in a shorter time because they are executed simultaneously.
     • Tasks can be shared to reduce the load on individual processors and avoid bottlenecks.
   • Disadvantages
     • It is difficult to write programs for multicore systems, ensuring each task has the correct input data to work on.
     • Results from different processors need to be combined at the end of processing, which can be complex and adds to the time taken to execute the program.
     • Not all tasks can be split along multiple processors.

3. Structure and Function

   • What factors affect processor performance?
     • Clock Speed
       • The control unit uses a clock to manage the Fetch-Decode-Execute Cycle.
       • One 'tick' on the clock is 1 run through of the FDE Cycle.
       • Measured in Hertz, 1 Hertz is 1 FDE Cycle per second (Hertz measures frequency).
       • MegaHertz (MHz) = 1 Million per second Gigahertz (GHz) = 1 Billion per second
       • A faster clock speed means more instructions can be processed per second which makes a faster CPU.
     • Number of Cores
       • Advantages
         • More jobs can be done in a shorter time because they are executed simultaneously.
         • Tasks can be shared to reduce the load on individual processors and avoid bottlenecks.
       • Disadvantages
         • It is difficult to write programs for a multicore system, ensuring that each task has the correct input data to work on.
         • Results from different processors need to be combined at the end of processing, which can be complex and add to the time taken to execute a program.
         • Not all tasks can be split access multiple processors.
     • Cache
       • Cache memory is high-speed memory that holds the most recent data and instructions that have been loaded by the CPU.
       • Cache is located directly on the CPU, making it faster to access than normal RAM.
       • Cache is made of very high-speed components. Having a cache reduces the number of fetches for both instructions and the data.
       • Cache is also very expensive for something of such a small size.
     • Overclocking
       • This is where you run your CPU at a faster speed than what was intended out of the box.
         • Advantages
           • You can buy a computer with a lower processor (which is cheaper) and make the processor faster on your own.
           • It gives a better performance in programs used for games and video editing.
         • Disadvantage
           • The device could overheat and cause problems with other parts of your device.
           • Your warranty on your device could then also become void and you would be unable to send it back as your have changed/tampered with the settings.
     • RAM
     • Register Size
     • Data Bus