Comp2- Machine architecture Flashcards
Which unit in the processor does calculations and whats it made of?
Arithmetic logic unit
made of circuits.
What calculations does the arithmetic logic unit do? (5)
adding, subtraction, fixed point and floating point arithmetic, Boolean logic, shift operations.
What does the program control unit do.
fetches program instructions from memory, decodes them and executes them one at a time.
Whats in the program control unit?
Instruction decoder, Program counter, Current instruction register , control circuits and the status register.
What are registers?
fast memory locations inside the processor(or I/O controller) they can be dedicated or general purpose.
How are general purpose registers accessed?
through instructions such as LOAD,STORE and ADD.
What does the stack point (SP) dedicated register do?
points to a stack holding return addresses, procedure or function parameters, and local variables, accessed when a procedure or function is called.
What does the program counter (PC) dedicated register do?
points to the next instruction to be fetched and executed.
What does the status register (SR) dedicated register do?
Holds conditional codes to indicate the outcome of operations. eg sign,zero, overflow,carry flags are set accordingly . (a series of bits, one for each flag.)
What does the accumulator (ACC) dedicated register do?
holds the result of the current set of calculations, eg ADD #36 , adds 36 to the contents of the accumulator.
how are general purpose registers labeled?
R0, R1, etc
What does the current instruction register(CIR) do/hold?
holds the current instruction to be executed while it is decoded and executed.
What does the memory address register(MAR) do/hold?
holds the address of the memory location currently being accessed by the processor.
What does the memory buffer register(MBR) do/hold?
holds the data item being transferred to or from the memory location currently being accessed.
what is a general purpose register?
a register not assigned a specific role by the processor designer, programmers may use them.
what is a dedicated register?
a register assigned a specific role by the processor designer. programmers may use some but not all dedicated registers.
What does the clock do?
each cycle of it triggers one step in the fetch execute cycle.
what do the control circuits do?
send the control signals down the control bus, eg read , write.
How does clock speed effect performance?
A higher clock speed means more instructions can be fetched and executed every second.
how does word length effect performance
the bigger the word length , the bigger the operands results can be accommodate. if the result exceeds the word length extra processing must be done to split operands and results across different registers which slows it down.
word length in the MAR and PC effects how much addressable memory there is.
what is clock speed
the clock speed of a processor is the frequency in MHz or GHz at which the processor executes instructions.
what is word length
The number of digits in a binary word.
what is bus width
The number of signal wires/ lines allocated to a bus.
how does memory bus width effect performance
More addressable memory.
how does data bus width effect performance
More bits of data can be transferred along the bus in one go which should improve performance as less cycles have to happen to transfer the same amount of data.
What is a multicore processor and how does it effect performance?
More then one microprocessor on the same chip. with multiple cores (processors) multiple tasks can be run at once or a single task can be split among many cores.
What is cache memory and how does it improve performance?
Cache memory is a small amount of very fast SRAM located near/on the processor core. When a memory location is accessed a whole chunk of nearby data is loaded into the cache, it takes advantage that the next bits needed are in the next memory addresses.
