Computer Organisation Flashcards
What is the i/o system?
Allows the computer to communicate with the outside world and store data while the power is off
Give an example of non-storage devices?
Keyboard, mouse, monitor, and speakers
Give another name for a storage device?
Auxilary device and they are categorized as either magnetic or optical
How optical and magnetic storage work
pg 98-104
How are the CPU and memory connected?
BY three groups of connections; each carrying one bit at a time. The number of connections depends on the size of the data being transferred.
What is the address bus?
It allows access to the memory.
The number of connections depends on the address space of the memory.
What is the data bus?
Its made of several connections; each carrying one bit at a time. The number of connections depends on the size.
What is the control bus?
Carries communication between the CPU and memory so there is a code sent from the CPU to memory to request a read/write operation.
The number of connections is determined by the number of control commands.
The computer needs 2^m control actions, we need m connections
How are I/O devices connected to the CPU and memory?
Through controllers which can be parallel or serial.
Give examples of controllers?
SCSI, FireWire, USB, and HDMI. More information on pg 106-108
What does a machine cycle consist of?
Fetch, decode, and execute
Explain the fetch phase
- The control unit orders the system to be copied into the instruction register.
- The address of the instructions to be copied is held in the program counter register.
- Once copying is done, the program counter is incremented to execute the next instruction.
Explain the decode phase?
Once the instruction is in the instruction register it is decoded by the control unit into binary code so the system can perform an operation with it.
Explain the execute phase?
The control unit will tell the system to read or use ALU to form operations with it.
What is programmed I/O?
The transfer of data between CPU and I/O device as the CPU constantly checks I/O waiting for data to transfer it. It does nothing else until the transfer is complete.
What is the interrupt-driven I/O?
The I/O device will interrupt the CPU when ready to transfer data allowing the CPUs time not to be waisted. Some as programmed I/O data goes to memory after input, data is from memory before output.
What is DMA?
Direct memory access is used to transfer large blocks of data between high-speed I/O devices (like a disk) without using the CPU. The DMA controller manages the data as it has registers to hold on to a block of data; the CPU will send a message containing the type of transfer (input/output), the beginning address of the memory location, and the number of bytes to be transferred. DMA allows the CPU to do other tasks and it will tell the CPU when it needs access to the buses. The CPU will start idling allowing the controller to make its transfers.
What is CISC? (complex instruction set computer)
The strategy behind the architecture is for programming to be easier as there is a single instruction for complex and simple tasks. The architecture has a large set of complex and single instructions this makes the CPU and control unit very complicated. eg Pentium
How do you reduce the complexity of the CPU and control unit in CISC?
The CPU only does simple operations and if there is a complex operation it is broken down into simple operations(micro-operations). Allowing micro-operations requires memory (micro-memory) to hold the set of complex operations.
What is RISC?
‘Reduced instruction set computer’ is to have a small set of instructions that do a minimum amount of operations. Complex instructions are broken down into subsets. Programming in RISC is more complex and time-consuming than the other ways.
What does the CPU consist of?
ALU, control unit, and a set of registers.
