PC Components: CPU, Memory, and Bus Systems

Posted on Dec 12, 2024 in Computers

**Process Control Unit**

The Process Control Unit is responsible for the implementation and monitoring of operations performed within the computer to process data. Processor speed is measured in megahertz (MHz) or gigahertz (GHz). The processor consists of two main parts:

  • Control Unit: The thinking part of the computer, controlling the overall operation of all components.
  • Arithmetic-Logic Unit (ALU): Responsible for performing arithmetic and logical operations.

Control Unit

The Control Unit is the nerve center of the PC, as it controls all operations. To perform its function, it includes the following elements:

  • Program Counter Register: Contains the memory address of the next instruction to execute.
  • Instruction Register: Contains the statement that is currently being executed.
  • Decoder: Responsible for extracting and analyzing the operation code of the current instruction.
  • Signal Generator or Sequencer: This device generates basic commands synchronized with the clock pulse, causing it to run step-by-step.

Arithmetic-Logic Unit (ALU)

This unit is responsible for performing basic arithmetical and logical operations. To perform these functions, it includes:

  • Register Bank: 8, 16, or 32 general registers used to locate data before each operation, store intermediate data during operations, and handle internal processor operations.
  • Operator Circuits: Composed of one or more electronic circuits that perform basic arithmetic and logical operations.
  • Result Register or Accumulator: A special register where the results produced by the circuit operators are deposited.
  • Status Register or Status Flags: A register with a set of flip-flops indicating certain conditions that occurred in the last operation performed.

Memory

Memory refers to any device that stores information for later use. Main memory keeps data and instructions that the CPU is currently using. External storage devices store information to be transferred to the main memory for use by the computer.

  • Memory Address Register (MAR): Contains the memory address where information is or will be stored, whether it is a read or write operation.
  • Register Memory Buffer Register (MBR): In a read operation, the MBR receives the data from the memory location specified by the MAR. In a write operation, the information to be written must be in the MBR to be transferred to the memory location indicated by the MAR.
  • Memory Selector: After a read or write order, this device connects the memory cell (whose address appears in the MAR) with the MBR, allowing data transfer in either direction.

Types of RAM

  • DRAM (Dynamic RAM): Requires refreshing to retain data; large capacity.
  • SRAM (Static RAM): Does not need refreshing; lower capacity and very fast.
  • SDRAM (Synchronous DRAM): Designed to synchronize with the CPU’s timing.
  • DDR (Double Data Rate): Enables the memory chip to make transitions on both the rising and falling edges of the clock cycle.
  • DDR2 (Double Data Rate 2): Makes two transitions on the rising edge and two on the falling edge of the clock cycle.
  • VRAM (Video RAM): Used by the graphics controller to handle all visual information sent by the system CPU.
  • SGRAM (Synchronous Graphics RAM): High capacity, high speed, and low power consumption.
  • CDRAM (Cache DRAM): Acts as a buffer between the processor and peripherals.

ROM

  • ROM (Read-Only Memory): Read-only memory.
  • PROM (Programmable ROM): Can be programmed once using a special programmer.
  • EPROM (Erasable PROM): Erasable and programmable memory.
  • CMOS (Complementary Metal-Oxide-Semiconductor): Low-power memory that stores the date, time, and BIOS settings.

Buses

A bus is a set of physical wires used for data transmission between components of a computer system. There are several types, classified according to their structure:

  • Single Bus: Memory locations are used to communicate with peripherals and the processor.
  • Dedicated Bus: Memory and peripherals are treated as two separate components.

Depending on functionality:

  • Data Bus: Transmits data between the CPU and peripherals.
  • Address Bus: Identifies the device targeted by the information on the data bus.
  • Control Bus: Organizes and redirects information to the bus according to the relevant data stream.

The type of bus incorporated into a computer directly affects its speed. The bus is characterized by the number and arrangement of its lines.