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The Computer System, REMEMBER - Coggle Diagram
The Computer System
Computer functions
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Computer Organization
Computer organization refers to the operational units and their interconnection that realize the architecture specification
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Example: Design Issue
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Organisational issue
▪ Instruction will be implemented by a special multiply unit or by a mechanism that makes repeated use of the add unit of the system
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Interconnection
System Interconnection
• Some mechanism that provides for communication among CPU, Memory and I/O
• A common example of system interconnection is mean by of a system bus, consisting of a number of conducting wires to which all the other computer attach
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Bus Interconnection
• A communication pathway connecting two or
more devices.
• Often grouped:
– A number of channels in one bus
– Eg: 32 bit data bus is 32 separate single bit
channels.
– Data bus, address bus, control bus
System Bus
• A system bus consists, typically of from about 50
to hundreds of separate lines.
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• System bus is a bus that connects major
computer components (processor, memory, I/O).
• The most common computer interconnection
structures are based on the use of one or more system buses
Data Bus
• A collection of wires through which data is transmitted
from one part of a computer to another is called Data Bus
• Data Bus can be thought of as a highway on which
data travels within a computer.
• This bus connects all the computer components to the
CPU and main memory
• The size (width) of bus determines how much data can
be transmitted at one time. E.g.:
A 16-bit bus can transmit 16 bits of data at a time.
32-bit bus can transmit 32 bits at a time.
• Width (number of lines) is a key determinant
of performance
– Because each line can carry only 1 bit at a time
– 8, 16, 32, 64 bit
• Example:
– data bus is 32 bits wide and each instruction is 64
bits long
– processor must access the memory module twice
during each instruction cycle
Address Bus
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• The size of address bus determines how many unique
memory locations can be addressed
Example:
A system with 4-bit address bus can address 2^4 = 16
Bytes of memory.
A system with 16-bit address bus can address 2^16 =
64 KB of memory.
A system with 20-bit address bus can address 2^20 = 1
MB of memory
• Identify the source or destination of data
– E.g: CPU needs to read an instruction (data) from
a given location in memory.
• Example:
– Processor wishes to read a word (8,16 or 32 bits)
of data from memory, it puts the address of the desires word on the address line
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Control Bus
• The connections that carry control
information between the CPU and other devices within the computer is called Control
Bus.
• The control bus carries signals that report the
status of various devices
Example: This bus is used to indicate whether
the CPU is reading from memory or writing to memory
Bus Width
• The width of the data bus has an impact on
system performance:
—The wider the data bus, the greater the number of
bits transferred at one time
• The width of the address bus has an impact on
system capacity:
—The wider the address bus, the greater the range
of locations that can be referenced.
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• Control unit is the one that will manage / control
which instruction set to be executed in which order
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