Processor Components

Processor Components

1. Motherboard

   • Everything in a computer is somehow connected to the motherboard, either through slots, wires, connectors or readouts; everything needs to connect to the central board.
     • It acts as an interface for all components though not all components are connected to it in the same way.
       • For example, the peripheral component interconnect express lanes that are used to connect devices such as graphics cards are not the same as those used to connect hard drives.

2. Power supply

   • It provides and regulates the supply of power to the motherboard and subsequently all other components.
   • Modern PSUs allow the computer to control when it turns on and off and allow power saving modes.

3. Arithmetic Logic Unit (ALU)

   • Carries out logical calcualtions such as addition, multiplication and etc.
   • It can also make logical comparisons between items of data for example, it can determine if one value is greater than another.

4. Control Unit (CU)

   • Governs the operation of all hardware including input and output devices and the CPU.
     • It does this by fetching, interpreting and executing each instruction in turn, in an automatically controled cycle.

5. Registers

   • Program Counter (PC)
     • Holds the address of the next instruction to be executed. When a sequence of instructions is to be executed the PC is automatically incremented to the point to the next instruction.
     • Depending on the length of the instruction 1,2 or 3 has to be added to its content unless the instruction is a jump so the destination address is used.
   • General Purpose registers (AX, BX, CX and DX)
     • They are used for performing general arithmetic functions. They have no predefined role by the chip designer and therefore can be manipulated by a computer programmer to perform the role of any other registers.
   • Memory Buffer (MBR)
     • Values that are about to be added or subtracted can be copied through the MBR into accumulators.
     • All the communications between the CPU and the memory take place through MBR.
   • Memory Address (MAR)
     • When the instruction is fetched from the memory the CPU places the address of it in the MAR and then carries out a memory read and the instruction is copied into MBR.
   • Current Instruction (CIR)
     • After the CPU carries out the memory read and copies the instruction from MAR to MBR the instruction is copied into CIR.

6. Clock

   • Ir regulates all the actions that take place. It provides a regular pulse of high voltage followed by a low voltage.
     • Each high to low transition is known as a cycle and it implements an instruction.

7. Buses

   • Data Buses
     • Carry the data being exchanged around a system in their binary from.
     • It is likely to have the largest word size as actual information will be the majority of the data that needs to be sent via the bus.
   • Address Buses
     • Carry the information about where the data is being sent.
   • Control Bus
     • Carries the signal that regulates data flow around a system. It is also concerned with timing operations such as memory writing, memory reading and I/O operations.
   • Peripheral Component Interconnect (PCI)
     • This is the bus to which most of the other components and buses in a modern PC are connected.
     • Runs at 33 MHz with a bandwidth of 132 Mbps.
     • It is much faster than the old ISA standard which only allows 8 Mbps.