Computer Systems: Hardware

Computer Systems: Hardware

1. Embedded systems

   • a computer system built within a larger device, e.g. digital cameras
   • built for a range of specific tasks, but are limited to a certain number of tasks
   • all of the components (microprocessor, memory, input & output interfaces) are on a single printed circuit board
     • the memory contains the program and this board is then built into a larger device

2. Computer Systmes

   • microprocessor is responsible for executing the instructions given to it in a program
     • microprocessor relies on other devices to allow users to input the instructions, to store the instructions, to transfer the instructions to carry them out and to carry out the commands it issues
     • it needs input devices (keyboards, mouse, etc) to provide it with data. Memory to store instructions. Permanent long-term memory, e.g. hard disk drives). Output devices, e.g. monitors, printers, etc. Bundles or wires (called buses) to transmit data from one component to another
       • these components are all referred to as hardware
   • computers need hardware and software. It basically 'wakes up' the computer and tells the microprocessor how to communicate with all the other devices.
     • it can use the application software such as spreadsheets. Application software are programs that perform specific tasks

3. CPU

   • Central Processing Unit
   • the way it is designed and carries out instructions is known as the 'Von Neumann Architecture'
     • the fetch-decode-execute cycle
       • before the cycle starts, the program instructions are copied from a storage device, e.g. DVD, to the RAM (Random Access Memory)
       • Fetch: instructions and data are moved from the RAM to the CPU
       • Decode: the CPU interprets the instructions and decides what action to perform
       • Execute: instructions are carried out
   • controls other devices, executes instructions and processes the data
   • RAM is where data is stored so that it can be retrieved quickly by the CPU. It is volatile because when there is no electrical power then the RAM loses all of its data
   • ROM (Read Only Memory). BIOS (Basic Input/Output System) is stored on ROM. Data on the chip cannot be changed. ROM is not volatile (remember ROM-NON-VOL)
   • Buses: collection of wires that carry signals between the various components of the computer system

4. Components of the CPU

   • Registers: storage locations within the CPU. They can be accessed more quickly than the RAM. Some of the registers are the accumulator (ACC), the program counter (PC), the memory address register (MAR), the instruction register (IR), memory data register (MDR).
   • Arithmetic and Logic Unit (ALU): carries out activities like addition, subtraction, multiplication, division, logical tests using logic gates and comparisons (such as if one number is bigger than another)
   • Control Unit (CU): monitors communications between the hardware attached to the computer. Controls input & output data, checks that signals have been delivered successfully, makes sure that data goes to the correct place at the correct time. Main elements are the clock and the decoder.
     • The Clock: pulses are sent to other components to coordinate their activities and ensure instructions are completed. Timing is controlled by a vibrating quartz crystal. Higher the clock speed, the faster the CPU. It is measured in cycles per second
     • The Decoder: decoded the program instructions that have been brought from the memory. Then sends control signals to the other component to carry the instructions out.

5. Pipelining

   • This allows processors to process more than one instruction at a time
   • speeds up the execution of the program but the problem of coordination can still be a problem because each stage may not take the same time to implement the instructions.

6. Microprocessor Performance

   • Clock Speed: the rate in which instructions are processed. Faster the clock speed, faster the rate of processing
     • instructions are processed by transistors. Their rate of processing has not become faster.
     • microprocessor produces a lot of heat and this increases with the clock speed. There are limits to the rate of cooling

7. Multi-core processors

   • It has more than one CPU and is supposed to increase processing speed.
   • The advantages are that the cores can work together on the same program (parallel processing). The cores can work on different programs at the same time
   • 1 core = single-core. 2 cores = dual-core. 4 cores = quad-core. 5 cores = penta-core. 8 cores = octa-core. 10 cores = deca-core