![]() ![]() The concept can be pushed further, though, with some specialized processing cores offering four or even 8 “cores” on a single physical core. Note: All consumer CPUs that utilize virtual cores only add one virtual core to each physical core. This conceptual second core is referred to as a virtual core. In the underlying CPU architecture, however, only one physical CPU core exists. The secondary pipeline is essentially advertised to the operating system as another CPU core. This concept is marketed as SMT ( Simultaneous MultiThreading) in AMD CPUs and Hyperthreading in Intel CPUs. This doesn’t add too much complexity to the CPU but enables increased performance by filling in any gaps in the pipeline. This pipeline offers instructions to operate immediately if the main pipeline is otherwise halted. However, this issue can be easily overcome by having a secondary pipeline in place. This leads to a pipeline bubble or a pipeline stall. Instructions in the pipeline may need to be paused for one or more clock cycles while the CPU cache is consulted for data. Unfortunately, like everything, it’s not quite that simple. The pipeline is designed to keep instructions flowing through the CPU as efficiently as possible. But the performance boost is more than worth it. To make good use of a pipeline, a little more effort does need to go into designing the CPU. This approach is called pipelining, and it can achieve a significant performance increase over completing each instruction in full before moving on to the next one. The significant advantage of doing so is that you can use all of the segments of the pipeline at once. However, having these circuits be distinct doesn’t need to be as strictly linked in their actual usage. The actual circuitry for the CPU core has several distinct parts each part corresponds to a stage of the execution of an instruction. This is a simple design, but it’s not very efficient. It would also fully complete each instruction before moving on to the next one. The CPU core would complete the instructions in the order it received them. Early designs of CPUs only used one CPU core and were fundamentally sequential in operation. ![]()
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