Computer System Admins - 1.2 Processor and other components

What is a Processor

• Definition: A processor is an important part of a computer that performs tasks. It takes instructions, does calculations or logical operations, and produces output.

Basic Functions of a Processor

• Calculations: It can add, subtract, multiply, and divide using its special part called the Arithmetic and Logic Unit (ALU).

• Data Movement: The processor can move data from one place to another inside the computer.

• Next Instruction Tracking: It has a register called the Program Counter (PC) that keeps track of which instruction comes next.

Key Parts of a Processor

• Control Unit (CU): This directs everything in the processor, deciding how data flows and fetching the instructions.

• Arithmetic and Logic Unit (ALU): This part does all the math and logic operations, like calculations and comparisons.

Memory Units in a Processor

• Accumulator (ACC): Stores the results of calculations.

• Program Counter (PC): Remembers where the next instruction is located in memory.

• Memory Address Register (MAR): Stores the address of instructions that are needed from memory.

• Memory Data Register (MDR): Holds the instructions or data that have been fetched from memory.

• Current Instruction Register (CIR): Contains the most recent instruction that’s ready to be executed.

• Instruction Buffer Register (IBR): Holds instructions that aren't executed immediately

Input/Output Devices

• Input devices bring data into the computer (like a keyboard), while output devices send information out (like a monitor)

Buses in a Processor

• Data Bus: Carries actual data between the memory, input/output devices, and processor.

• Address Bus: Carries addresses (locations) of data between memory and the processor, but not the data itself.

• Control Bus: Sends commands from the CPU to control and coordinate activities within the computer.

Memory

• Internal Memory: This is where data and instructions are stored. It's also called primary or main memory, often referred to as RAM (Random Access Memory). RAM allows data to be accessed quickly regardless of its location.

I/O Modules

• I/O Interface: This manages the way data transfers between the CPU and external devices. It acts as a bridge to help the CPU communicate with other parts of the computer

Modes of Data Transfer

• Programmed I/O: The program controls the data transfer using specific commands. The CPU has to keep checking the devices to see if they’re ready.

• Interrupt-Initiated I/O: The CPU can continue working on other tasks while waiting for devices to signal that they’re ready for data transfer. When a device is ready, it sends a signal (interrupt) to the CPU, which then pauses its current task to handle the request.

• Direct Memory Access (DMA): This allows devices to transfer data directly to and from memory without needing the CPU. This speeds up the process since the CPU doesn’t need to manage each transfer.