Comp Hardware ( 2 ) Flashcards
(22 cards)
What is the I/O controller?
- Device which interfaces between an input or an output device and the processor.
- Each device has a separate controller which connects to the control bus.
How do I/O controllers function?
- I/O controllers receive input and output requests from the processor, and then send device specific control signals the device they control.
- Manage the data flow to and from the device.
What is the controller?
Controller is an electronic circuit board consisting of three parts
What three parts does the controller consist of?
- Interface that allows the connection of the controller to the system or I/O bus
- A set of data, command and status registers
- An interface that enables connection of the controller to the cable connecting the device to the computer.
What is an interface?
Standardised form of connection defining such things as signals, number of connecting pins/sockets and voltage levels that appear at the interface.
What is the stored program concept?
Machine code instructions are fetched and executed serially by a processor that performs arithmetic and logical operations.
What are the requirements of the stored program concept?
- A program must be resident in main memory to be executed
* Machine code instructions are fetched from main memory one at a time, decoded and executed in the processor.
What occurs in embedded systems?
- Instructions may be held in read only memory while data memory requires read write memory.
- There is much more instruction memory than data memory so the instruction addresses and address bus are wider than the data addresses and data bus.
what are some features of embedded systems?
They include special purpose computers built in to devices often operating in real time, such as those used in navigation systems, traffic lights or flight control systems.
Why is Harvard architecture faster than von neumann architecture?
Data and instructions can be fetched in parallel instead of competing for the same bus.
What is the purpose of the control unit?
Controls and co-ordinates the activities of the CPU, directing the flow of data between the CPU and other devices, accepts the next instruction, breaks down its processing into sequential steps such as fetching addresses and data from memory, manages its execution and stores resulting data back in memory.
What is the purpose of the system clock?
Generates a series of signals, switching between 0 and 1 billions of times per second - synchronisation of CPU operations.
What is an accumulator?
General purpose register, only used when there is just a single register in which to store the result of each calculation or logical expression.
What is the purpose of the status register?
• Contains bits that are set or cleared depending on the result of an instruction.
What is the fetch execute cycle?
Sequence of operations involved in executing an instruction can be divided into three phases, cycle is repeated as each instruction of the program is executed.
What factors affect processor performance?
Number of cores linked together on a single chip • Amount/Type of cache memory • Clock speed •Word length • Address bus width • Data bus width
How do multiple cores benefit a processor?
Each core is able to process a different instruction at the same time with its own fetch execute cycle, making it two or even four times faster with a quad core chip.
What is a downside to using a multi core processor?
Not all applications fully utilise the multiple cores.
What is cache?
A very small amount of very fast, expensive memory inside the CPU.
How is the cache utilised?
- When an instruction is fetched from main memory, it is copied into the cache so if it is needed again soon after, it can be fetched from cache, which is much quicker than going back to main memory.
- As cache is utilised unused instructions or data still being held are replaced with more recent ones.
How does clock speed affect processor performance?
- All processor activities begin on a clock pulse
- Clock speed is measured in gigahertz
- Greater the clock speed, the faster the instructions will be executed.
When might an interrupt occur?
when an application program terminates or requests certain services from the operating system
