4 CPU Architecture Flashcards
(28 cards)
von neumann architecture
Instructions and data are stored in the same memory.
The CPU fetches both instructions and data from this shared memory.
what are the components of the cpu
ALU, CU, system clock, Immediate access store (IAS)
general purpose register
hold data that is frequently
used by the CPU e.g. accumulator
special purpose register
have a specific function within the CPU and hold the
program state.
current
instruction
register (CIR)
stores the current instruction being decoded and executed
Index register (IX)
stores a value that’s added to an address to give to another address
Memory addresses register (MAR)
stores the address of the memory location currently being read from
Memory data register (MDR)
stores data which has just been read from memory
Program counter (PC)
stores the address where the next instruction to be read can be found
Status Register
Holds flags (e.g. Zero, Carry, Overflow) to indicate results of operations.
Accumulator (ACC)
hold the results of arithmetic and logic operations
Roles of ALU, CU, System clock, IAS
Component Function
ALU Performs arithmetic and logic operations.
CU coordinate actions of others in the CPU operations, sends control signals to other CPU parts.
System Clock Controls timing, synchronizes all operations in CPU.
IAS (Immediate Access Store) Main memory used during processing for fast access.
address bus
carries addresses throughout the computer system.
Between the CPU and memory the address bus is unidirectional
data bus
data can be carried from CPU to memory as well as to and from input/output devices.
it is bidirectional
control bus
Bidirectional
Carries control signals (e.g. Read/Write).
Factors Affecting CPU Performance
Processor Type / Cores:
each core processes one instruction pe clock pulse
more cores = decrease time taken to complete task
Bus Width:
Wider buses = more data transferred at once.
Clock Speed:
each instruction is executed on a clock pulse
faster clock speed = more instructions can be run per second
Cache Memory:
stores frequently used instructions
Ports for Peripheral Devices
USB (Universal Serial Bus): Connects input/output devices like keyboard, mouse.
HDMI (High-Definition Multimedia Interface): Transfers video and audio to display devices.
VGA (Video Graphics Array): Older video output interface.
fetch decode execute
PC has the address of the memory location of the next instruction to be fetched
this address is copied from the PC to the MAR using the address bus
the instruction at the address contained in the MAR is copied temporarily to the MDR
the instruction if the MDR are copied into the CIR
The PC is incremented by one so it points to the next instruction which has to be fetched
the instruction is decoded and executed by sending signals via the control bus
Interrupts
detected at start/end of cycle
handled:
- priority is checked
- if lower priority than current process continue with F-E cycle
- if higher priority then registers are stored on stack
machine code
the programming language the CPU uses (binary)
Assembly language
Human readable mnemonics
opcode
operation to be carried out by the CPU
operand
identifies the data to be used by the opcode
two pass assembler
pass 1 :
removes comments
reads assembly language program one line at a time
check opcode is in the instruction set
pass 2 :
read assembly language program one line at a time
generate object code
