Computer Architectures Flashcards
What are the features of Von Neumann architecture?
- Fetch.Decode.Execute cycle
- One instruction processed at a time.
- Single control unit (manages program control)
- Programs are stored with data in the same format
Name the registers used by the processor.
- memory address register
- memory data register
- current instruction register
- accumulator
- interrupt register
- index register
Describe the fetch-execute cycle.
- PC holds address of next instruction
- copy contents of PC to MAR
- increment PC
- load instruction pointed to by the MAR to MDR
- copy instruction from MDR to CIR
- decode instruction in CIR
Describe how a jump instruction is executed.
copying address part of the instruction in CIR to the PC
Name six architecture types.
- Von Neumann
- Co-Processor
- Parallel Processor
- Array Processor
- RISC
- CISC
Describe a parallel processor system.
- More than one processor.
- Processors work together to perform a single job.
- Jobs are split into tasks.
- Each task can be processes by any processor/
- Processors are controlled by a complex operating system.
Describe an array processor.
- A processor that allows the same instruction to operate simultaneously on multiple data locations.
- It uses multiple ALUs.
- Single Instruction Multiple Data
- The same calculation on multiple data is very fast.
What does RISC stand for?
Reduced Instruction Set Computer
What does CISC stand for?
Complex Instruction Set Computer
State features of RISC?
- limited number of instructions available
- an instruction performs a simple task
- complex tasks can only be performed by combining a number of instructions
- complex tasks can take more than one machine cycle
Describe the use of the MDR.
- Instruction/data from address in MAR is copied to MDR
- instruction in MDR is copied to CIR
- MDR acts as a buffer/temporary store
- MDR contains data/instructions…
- …when being transferred between memory & processor
Explain the use of the accumulator in the processor.
- holds data being processed
- temporary storage of intermediate results (in the
ALU) - is where calculations are performed
- input & output data passes through
Explain the term register.
- a location in the processor
- used for a particular purpose
- (temporarily) stores data/or control information
- explained example of contents held by named register
Give the advantages of using parallel processor systems.
- allows faster processing
- more than one instruction (of a program) is processed at the same time
- different processors can handle different tasks/parts of same job
Give the disadvantages of using parallel processor systems.
- operating system is more complex…
- …to ensure synchronisation
- program has to be written in a suitable format
- Program is more difficult to test/write/debug
State features of Complex Instruction Set Computer.
- uses (complex) instructions each of which may take multiple cycles - single register set - instructions have variable format - many instructions are available - many addressing modes are available
What is the disadvantage of using CISC over RISC?
- programs run more slowly…
- …due to the more complicated instructions/circuit
How does the contents of MAR change during the fetch-execute cycle?
- Receives address of instruction/data (from PC)
- Holds address of data/instruction to be used
- Receives operand part of instruction from CIR.
How does the contents of MDR change during the fetch-execute cycle?
- Receives an instruction/data
- …from memory location in MAR
- Receives data/instruction from…
- …memory location in address part of instruction/accumulator.
