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Ch.11 The System Unit of a Computer System - Coggle Diagram
Ch.11 The System Unit of a Computer System
11.1 The Components of a computer
System Unit contains power supply, storage device and motherboard
Motherboard provides sockets for cpu, memory chp and expansions cards for additional boards, contains circuity that connect the parts together
Peripherals are the hardware device connected to the system unit
11.2 Central processing unit
Accumulate the instructions of a computer program, processes data to do a specific tasks
The processing power of the CPU usually determines the overall performance of a computer
CPU communicates with other devices through bus lines
Central Processing Unit(CPU)
Arithmetic and logic unit(ALU)
Results are usually stored in a register called an accumulator
Perform arithmetic and logical operations
Use registers to hold data during calculations
Control Unit(CU)
Keep track of the sequence of instructions being processed
Monitors and coordinates all I/O operations and system units
Register
Memory units inside a CPU
Provide storage space for ALU and CU
Small number of registers
Fastest way for a CPU to access data
System Bus(Bus Line)
Data bus
Transfer data and instructions
Address bus
Transfer the source address or the destination address of data
Control bus
Indicate the direction of the data transfer and coordinate the timing of the event during transfer
Size of a bus = bus width
Bus width determines the number of bits of data the computer can transmit at one time
11.3 Machine Cycle
Process of executing an instruction in a CPU
Sub-cycle
Execute
interpret the operation code and perform the required operation
Fetch
Read the next instruction from the main memory into instruction register(IR)
Decode
Identify the operation code and operands in an instruction
11.4 Measurement of CPU Speed
Clock Rate
Measurement unit:megahertz(MHz) or gigahertz(GHz)
1 Hertz = 1 clock cycle per second
Measure speed of CPU
Word length
Number of bit of data and instruction can handle at one time
Advantage of long word length
More data can be processed in one time
More instructions can be included in the instruction set
More complicated instructions can be included in the instruction set
11.5 Main Memory
Used to store data or instruction that CPU will execute
2 major types: Random Access Memory and Read-Only Memory
The memory chips are installed on the motherboard
RAM
Temporarily hold the data and instructions of application software and the operation system
Volatile = all data stored in RAM disappears instantly after the PC is turned off
Access time is just a hundredth of hard disk
Measurement unit: bytes(B), kilobytes(KB0, megabytes(MB),gigabytes(GB),terabytes(TB)
Two main streams
Dynamic DRAM
Static SRAM
Accessible to the CPU of a computer without using other I/O channels
Read-only memory
Store the permanent information supplied by the manufacturer
Contain the bootstrap program which loads and initializes the operation system of the computer
Store basic input/output system(BIOS)
Non-volatile
Two types
Erasable Programmable ROM(EPROM)
Electrically erasable programmable ROM(EEPROM)
Cache Memory
High-speed memory
Store data and instructions that have been recently used by the CPU
CPU requests an instruction:
Searches cache memory first in a very short time
Found
Acquires the data and proceeds to the next task
Not found
Look up in the main memory
Integrated into a CPU or resided close to a CPU
11.6 Latest Development of CPU and Main Memory
The future development of the CPU in the future has focused on the integration of more cores into the CPU