https://www.youtube.com/watch?v=HA96GwuvdVM

The Central Processing Unit Lesson Objective: Understanding the CPU Learning Outcome: Define the keywords Describe fetch-decode-execute Why Cache is preferable to RAM How clock speed and cores affect performance Keywords: CPU, Cache, Fetch-decode-execute, clock speed, dual-core, quad-core.

Lets play cards!

CPU Instruction Cache Data Cache RAM Storage Device (Backing store) Instructions

Inside the CPU The CPU can only process one simple instruction at a time Each instruction is ‘Fetched’, ‘Decoded’ then ‘Executed’ The speed of the fetch-decode-execute cycle is determined by the clock speed

The CPU clock speed The speed is usually measured in GHz (GigaHertz) 1 GHz = 1000 Million cycles per second Think of this happening for each step of the fetch-decode-execute cycle.

Imagine the process like this:

CPU Multi-Core processors 2 processors = Duo 4 processors = Quad To prevent writing to the same location, each core needs its own cache. Core 2 Some tasks can be done much quicker with multiple processors Individual Cache Individual Cache Shared Cache

i7 = Quad (but can seem like more due to ‘clever stuff’!) Core processors In the exam you may be given specifications like this: 1.2 GHz Duo Processor In real life you will see specifications like this: Intel 2.5 GHz Core i7 i3 = Duo I5 = Quad i7 = Quad (but can seem like more due to ‘clever stuff’!)

Which computer will give the better performance?