Computer Data Conversion
Topic: Computer Data Handling and Processing
Class: SSS Two
Introduction
Computers process and manage vast amounts of data. To understand how a computer works, it's essential to know how data is stored, moved, and processed internally. This section introduces key components and concepts that enable efficient data handling and execution of instructions within a computer system.
Definition of Terms
Data Conversion
Data conversion is the transformation of computer data from one format to another. This can include preparing data for processing, moving it between different storage types, or changing its representation (e.g., from text to binary for internal processing).
Registers
Registers are special, high-speed storage areas located directly within the Central Processing Unit (CPU). They are not part of the main memory but serve as additional storage locations that offer the advantage of extreme speed. Registers work under the direction of the control unit to accept, hold, and transfer instructions or data, and to perform arithmetic or logical comparisons at very high speeds. They are the fastest memory available for use in a computer, being hard-wired directly into the processor logic.
Address
A memory address is a unique identifier for a specific memory location where a computer program or a hardware device can store data and later retrieve it. It's like a house number in a very large street of memory.
Bus
A bus is a set of physical connections (like cables or printed circuits on a motherboard) that can be shared by multiple hardware components to communicate with one another. The primary purpose of buses is to reduce the number of individual "pathways" needed for communication between components by carrying out all communications over a unified channel. This is why the metaphor of a "data highway" is often used. If only two hardware components communicate over a dedicated line, it is typically called a hardware port (such as a serial port or parallel port).
A bus is characterized by two main properties:
1. Width: This is the amount of information that can be transmitted at once, expressed in bits. It corresponds to the number of physical lines over which data are sent simultaneously. For example, a 32-wire ribbon cable can transmit 32 bits in parallel.
2. Speed (Frequency): This is defined by its frequency (expressed in Hertz), which is the number of data packets sent or received per second. Each time that data is sent or received is called a cycle. By multiplying its width by its frequency, it is possible to find the maximum transfer speed (bandwidth) of the bus, which is the amount of data it can transport per unit of time.
Example 1: What is the speed of a bus with a width of 16 bits and a frequency of 133 MHz?
Solution: We need to find the bus speed (bandwidth). Given:
- Width = 16 bits
- Frequency = 133 MHz
Types of Computer Buses
Internal Bus (Front-Side Bus - FSB): This bus connects the processor to the system's central memory (RAM). While the term FSB is less common in modern architectures which use direct CPU-to-memory interconnects, the concept of a high-speed link for CPU-RAM communication remains fundamental.
Expansion Bus (Input/Output Bus): This bus allows various motherboard components (like USB ports, SATA ports for hard drives/CD-ROMs, and PCI/PCIe connectors for expansion cards) to communicate with one another and with the rest of the system. It is also used to add new devices via expansion slots.
Address Bus: Carries memory addresses from the processor to other components such as primary storage and input/output devices. The address bus is unidirectional, meaning data (addresses) only moves in one direction, from the CPU to the memory/devices.
Data Bus: Carries the actual data between the processor and other components. The data bus is bidirectional, meaning data can move in two directions (to and from the CPU).
Control Bus: Carries control signals from the processor to other components and vice-versa. For example, it transmits signals like "read," "write," "memory request," or "interrupt request." The control bus is bidirectional.
Types of Registers and their Functions
There are many types of registers, each with a specific role in the CPU's operation. Some key examples include:
Memory Data Register (MDR): This register temporarily holds the data that is either to be stored in the computer's memory or data that has been fetched from memory.
Current Instruction Register (CIR): The CIR stores the instruction that is currently being executed or decoded.
Memory Address Register (MAR): The MAR holds the memory address of the data or instruction that the CPU wants to read from or write to.
Program Counter (PC): Also commonly called the Instruction Pointer (IP) or sometimes the Instruction Address Register, the PC is a special register that holds the memory address of the *next* instruction to be executed by the microprocessor after the current instruction completes.
Accumulator Register: This register is used for storing the intermediate results of arithmetic and logical operations performed by the CPU's Arithmetic Logic Unit (ALU).
Functions of Registers
Registers perform several critical functions within the CPU:
i. They hold the address of memory locations where the CPU wants to read or write data.
ii. They store the actual contents of data or instructions read from or written to memory.
iii. They are used to specify the address of a particular Input/Output (I/O) device.
iv. Registers are used for exchanging data between the I/O module and the processor.
v. They store current instructions being executed or decoded.
vi. Some specialized registers (like shift registers) allow the bits of their content to be moved to the left or right, enabling bit manipulation operations.
vii. They temporarily hold memory addresses of data and instructions during the execution phase.
viii. Registers store the results produced by the system's processing units.
Differences between Registers and Main Memory
| Register | Main Memory |
|---|---|
| Registers are located inside the processor (CPU). | Main memory is located outside the processor (CPU) but connected to it. |
| They are extremely fast. | They are slower than registers but faster than secondary storage. |
| They are very small in capacity (typically a few dozen to hundreds of bytes). | They are large in capacity (typically gigabytes). |
Fetch-Execute Cycle
The fetch-execute cycle (also known as the instruction cycle) is the fundamental process by which a computer's Central Processing Unit (CPU) executes a program instruction. It describes the sequence of steps the CPU follows to retrieve an instruction from memory, decode it, and then perform the operation it specifies.
The steps in the processing cycle are as follows:
Fetch the next instruction: The Program Counter (PC) contains the address of the next instruction to be executed. The Control Unit (CU) goes to this address in memory, retrieves a copy of the instruction, and places it into the Current Instruction Register (CIR).
Decode the Instruction: To execute the instruction in the CIR, the Control Unit interprets its operation code (opcode) to determine what action needs to be performed (e.g., addition, data transfer, branching).
Get Data (if needed): If the instruction requires data to be processed, the Control Unit fetches that data from memory and places it into an appropriate register (like the Memory Data Register). This might involve calculating the effective memory address of the data.
Execute the Instruction: Once the instruction is decoded and any necessary data is fetched, the Control Unit sends signals to the Arithmetic Logic Unit (ALU) or other CPU components to carry out the specified operation. When the execution is complete, the cycle begins again for the next instruction.
Fetch-Execute Cycle Flow Diagram
Factors Affecting Data Transfer Speed
Several key factors influence how quickly data can be moved and processed within a computer:
1. RAM Size: A larger RAM capacity generally leads to faster data transfer and processing. More data and programs can be loaded into memory for immediate access, reducing the need to access slower secondary storage.
2. CPU Speed and Generation: The clock speed of a CPU (measured in Hertz, Hz) indicates how many cycles it can perform per second. A faster CPU, along with its generation (which implies architectural improvements and more cores), can process more instructions and data much quicker, significantly improving overall data transfer and processing speed.
3. Register Size: Larger registers can hold more data at once. This means the CPU can process larger chunks of data in a single operation, potentially accelerating data transfer and computations.
4. Bus Width: A wider bus (more physical lines) can transmit more data bits simultaneously. This increased data transmission capacity directly translates to faster transfer rates between components.
5. Bus Speed (Frequency): A higher bus frequency allows data to be transferred more quickly by increasing the number of data transfer cycles per second.
6. Cache Memory: Cache memory is a small, very fast temporary memory that holds frequently accessed data and instructions. It acts as a buffer between the CPU and main memory. The larger and faster the cache memory, the less often the CPU needs to access the slower main memory, leading to significantly faster data access and processing. The downside of cache memory is that it trades off capacity for speed, being much more expensive per unit of storage than RAM.
wow! this is lovely and detailed.
ReplyDeleteGreat job. Keep it up!
ReplyDeleteYour work is great. But are you sure there are only 2 types of buses?
ReplyDeleteThere are 3 types
DeleteAddress bus
Control bus
Data bus
Great job
ReplyDeleteThanks
ReplyDeleteWow that's great
ReplyDelete