Simultaneous multithreading
As we learned in previous chapters, each executing process contains one or more threads of execution. When performing multithreading with time-slicing on a single-core processor, only one thread is in the running state at any moment in time. By rapidly switching between multiple ready-to-run threads, the processor creates the illusion (from the user’s viewpoint) that multiple programs are running simultaneously.
This chapter introduced the concept of superscalar processing, which provides a single processing core with the ability to issue more than one instruction per clock cycle. The performance enhancement resulting from superscalar processing may be limited when the active sequence of instructions does not require a mixture of processor resources that aligns well with the capabilities of its superscalar functional units. For example, in a particular instruction sequence, integer processing units may be heavily used (resulting in pipeline bubbles...
