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The Time Stamp Counter was once a high-resolution, low-overhead way for a program to get CPU timing information. With the advent of multi-core/hyper-threaded CPUs, systems with multiple CPUs, and hibernating operating systems, the TSC cannot be relied upon to provide accurate results — unless great care is taken to correct the possible flaws: rate of tick and whether all cores (processors ...
Some examples are (486→Pentium, in clock cycles): CALL (3→1), RET (5→2), shifts/rotates (2–3→1). A faster, fully hardware-based multiplier makes instructions such as MUL and IMUL several times faster (and more predictable) than in the 80486; the execution time is reduced from 13 to 42 clock cycles down to 10–11 for 32-bit operands.
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 ...
The number of instructions per second is an approximate indicator of the likely performance of the processor. The number of instructions executed per clock is not a constant for a given processor; it depends on how the particular software being run interacts with the processor, and indeed the entire machine, particularly the memory hierarchy.
The next instruction is in the same 1K-word region as the current instruction, because bits 11–10 remain the same. The CA field determines the 64-word block within the region. The instruction is in the same 4-word group within the new block as the current instruction is within the current block, because bits 5–2 remain the same.
CPU time (or process time) is the amount of time that a central processing unit (CPU) was used for processing instructions of a computer program or operating system. CPU time is measured in clock ticks or seconds. Sometimes it is useful to convert CPU time into a percentage of the CPU capacity, giving the CPU usage.
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.
Each CPU machine instruction takes up a certain number of clock cycles, usually equal to the number of memory accesses. For example, the absolute indexing mode of the ORA instruction takes 4 clock cycles; 3 cycles to read the instruction and 1 cycle to read the value of the absolute address.