Unlike individual reservation stations, a group or central reservation station, or a DRIS must be efficient in dispatching higher than one instruction in each cycle. In these cases, the design space needs an additional component that determines how many instructions can be dispatched from each of the reservation stations or ... Read More

The dispatch policy specifies how instructions are selected for execution and how to dispatch blockages are handled. The dispatch policy can be considered as a scheduling policy consisting of the components specified as shown in the figure.Selection Rule − The selection rule specifies when instructions are considered executable. Let us ... Read More

There are two types of operands fetch policies such as issue bound or dispatch bound. The issue-bound fetch policy defines that operands are fetched during instruction issues. In this method, shelving buffers influence instructions with their operand values, needing that the buffers be fully long to support space for all ... Read More

Shelving buffers have three major aspects such as the type and capacity of the buffers used and the number of their read and write ports, as shown in the figure.Types of shelving buffersThere are two generic types of shelving buffers such as standalone shelving buffers and combined buffers which are ... Read More

Shelving is an advanced issue mode, which is employed to eliminate issue blockages due to dependencies. Shelving makes use of dedicated instruction buffers, called shelving buffers, in front of each EU. Shelving decouples dependency checking from the instruction issue, and defers to it the dispatch phase.It can more precisely with ... Read More

A superscalar processor is created to produce an execution rate of more than one instruction per clock cycle for a single sequential program. Superscalar processor design generally defines a set of techniques that enable the central processing unit (CPU) of a computer to obtain a throughput of more than one ... Read More

The following methods used in instruction issue policies such as the scalar processors, superscalar processors, and the broad picture covering both. While considering the most frequently used issue policies, it can reduce the design space of instruction issues by ignoring less important aspects.First, for both scalar and superscalar processors, it ... Read More

The handling of issue blockages can be broken into two types as displayed in the figure. The first aspect called preserving issue order specifies whether a dependent instruction blocks the issue of subsequent independent instructions in the issue window. The second aspect is the alignment of instruction issue. It decides ... Read More

Superscalar instruction issue is the most sensitive task of superscalar operation. The issue policy determines how dependencies are managed during the issue process. The issue rate defines the maximum number of instructions a superscalar processor can issue in each cycle.The design space of issue policy is complex. As shown in ... Read More

A scalar processor has to decode only a single instruction in each cycle as shown in the figure. In addition, a pipelined processor has to check for dependencies to decide whether this instruction can be issued or not. In comparison, a superscalar processor has to perform a much more complex ... Read More