Search results
Results from the WOW.Com Content Network
The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch–execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions. It is composed of three main stages: the fetch stage, the decode stage, and the execute stage.
The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch-execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions. It is composed of three main stages: the fetch stage, the decode stage, and the execute stage.
The blue instruction, which was due to be fetched during cycle 3, is stalled for one cycle, as is the red instruction after it. Because of the bubble (the blue ovals in the illustration), the processor's Decode circuitry is idle during cycle 3. Its Execute circuitry is idle during cycle 4 and its Write-back circuitry is idle during cycle 5.
The first machine to use out-of-order execution was the CDC 6600 (1964), designed by James E. Thornton, which uses a scoreboard to avoid conflicts. It permits an instruction to execute if its source operand (read) registers aren't to be written to by any unexecuted earlier instruction (true dependency) and the destination (write) register not be a register used by any unexecuted earlier ...
The instruction unit (I-unit or IU), also called, e.g., instruction fetch unit (IFU), instruction issue unit (IIU), instruction sequencing unit (ISU), in a central processing unit (CPU) is responsible for organizing program instructions to be fetched from memory, and executed, in an appropriate order, and for forwarding them to an execution unit (E-unit or EU).
Various methods of speeding up the fetch-execute cycle include: designing instruction set architectures with simpler, faster instructions: RISC as opposed to CISC; Superscalar instruction execution; VLIW architectures, which make parallelism explicit
"Fetch" the instruction from its original location (if necessary) into the monitor's memory. If "trace" is available and "on", store program name, instruction offset and any other values. Depending upon the instruction type, perform pre-execution checks and execute.
In a Von Neumann architecture which uses the program counter (PC) register to determine the current instruction being fetched in the pipeline, to prevent new instructions from being fetched when an instruction in the decoding stage has been stalled, the value in the PC register and the instruction in the fetch stage are preserved to prevent ...