A bus is a communication path way connecting two or more devices.Take the motherboard and look at the bottom side of it, you can see lines connection to each element. That is a bus.
System bus
Connects the CPU with main memory and other system components.
Peripheral device
Device other than the CPU and primary storage.
Bus clock pluse
Common timing reference for all attached device.
Data tranfer rate
Rate at which data is transmitted through a medium or communication channel ,as a measurement in data unit per time interval.
Bus protokol
Set of rule which by data moves between devices.Eg : number of bit,number of address
Bus operation
To send data to another device
- First the module must get permission
to use the bus, and then only can send the data
To request data from another device
- First the module must get permission
to use the bus, and then send a request signal to
the other device and finally
wait for the device to send the data.
Internal/External Buses
System Bus
Addres Bus : Use to transfer address from PC to memory.
Data Bus : Carry data,instuction and address between main memory and ALU
Control Bus : Carry signal such as interrupt ,timing and acknowledgment to and from
component.
Single Bis problem
- Many device may share one single bus for their operation.
- This may lead to Propagation.
- Propagation delay is the time taken for a signal to travel from a point of input to a point of
output.
- Result will be measured in microsecond,etc
- To solve the problem use multiple busses
Bus Hierarchy
Addres Bus : Use to transfer address from PC to memory.
Data Bus : Carry data,instuction and address between main memory and ALU
Control Bus : Carry signal such as interrupt ,timing and acknowledgment to and from
component.
Single Bis problem
- Many device may share one single bus for their operation.
- This may lead to Propagation.
- Propagation delay is the time taken for a signal to travel from a point of input to a point of
output.
- Result will be measured in microsecond,etc
- To solve the problem use multiple busses
Bus Hierarchy
The Processor Bus
(System Bus):
This is the highest-level bus that is
used to send information to and from the processor.
The Cache Bus:
Higher-level architectures employ a
dedicated bus for accessing the system cache.
This is sometimes called a backside
bus.
The Memory Bus:
This is a second-level system bus that
connects the memory subsystem to the processor.
In some systems the processor and
memory buses are basically the same thing.
The Local I/O Bus:
This is a high-speed input/output bus
used for connecting performance-critical peripherals to the memory and
processor. For example, video cards, disk storage devices, high-speed networks
interfaces generally use a bus of this sort.
The Standard I/O Bus:
Used for slower peripherals (mice,
modems, regular sound cards, low-speed networking) and also for compatibility
with older devices.
The illustration show how the various busses connect to the CPU
Characteristic of Bus
Every bus is composed of two distint part : Data bus,Address bus and Control bus.
Data bus : The line that actually carry the data being transfered.
Address bus : Is the set of line that carry information about where in memory the
data is to be transfered to or from.
Control bus : Control line that control how the bus functions and allow user of
the bus signal when data is available.
Bus Width : The number of bit that can travel in parallel along the bus.
The wider the bus,the better it is since more data can flow at one time.
Bus Speed : How many bits can be sent within a second.
How fast the bits are following through the bus.
Bus Bandwidth : Also known as throughtput which refers to the total
amount of data that can be transfered on the bus in a given unit of time.
Bandwidth = Bus Speed x Bus Width.
Bus perfomance
Transfer time : Amount of time taken for data to be delivered in a single transaction.
Bandwidth : Measures the capacity of the bus.
How much can the bus sent at one time.
Bus standard
System board
