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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.
Blank line; Comment; Label declaration (with optional end-of-line comment) A-instruction (with optional end-of-line comment) C-instruction (with optional end-of-line comment) Each of these line types has a specific syntax and may contain predefined or user defined symbols or numeric constants. Blank lines and comments are ignored by the assembler.
In computer engineering, instruction pipelining is a technique for implementing instruction-level parallelism within a single processor. Pipelining attempts to keep every part of the processor busy with some instruction by dividing incoming instructions into a series of sequential steps (the eponymous "pipeline") performed by different processor units with different parts of instructions ...
Then, any topological sort of this graph is a valid instruction schedule. The edges of the graph are usually labelled with the latency of the dependence. This is the number of clock cycles that needs to elapse before the pipeline can proceed with the target instruction without stalling.
A hardware interrupt is a condition related to the state of the hardware that may be signaled by an external hardware device, e.g., an interrupt request (IRQ) line on a PC, or detected by devices embedded in processor logic (e.g., the CPU timer in IBM System/370), to communicate that the device needs attention from the operating system (OS) [7] or, if there is no OS, from the bare metal ...
The only way to clear the effects of an STP instruction is to toggle RESB. On the Zilog Z80, executing DI (disable interrupts) followed by HALT (wait for an interrupt) results in the CPU staying frozen indefinitely, waiting for an interrupt that cannot happen. However, the non-maskable interrupt signal can be used to break out of this state ...
The R8000 (1994) was the first superscalar MIPS design, able to execute two integer or floating point and two memory instructions per cycle. The design was spread over six chips: an integer unit (with 16 KB instruction and 16 KB data caches), a floating-point unit, three fully-custom secondary cache tag RAMs (two for secondary cache accesses ...
In interrupt-driven processors, this instruction halts the CPU until an external interrupt is received. On most architectures, executing such an instruction allows the processor to significantly reduce its power usage and heat output, which is why it is commonly used instead of busy waiting for sleeping and idling.