In this section, we are concerned with an important performance measure of pipelined load/store processing such as load-use delay. The value of the load-use delay is a characteristic attribute of pipelined execution of loads. Large load-use values can seriously impede processor performance, especially in a superscalar processor.Load-use delays arise from load-use dependency, a kind of RAW dependency. Load-use dependency gives rise to a load-use delay if the outcome of the load instruction cannot be made accessible by the pipeline in due time for the subsequent instruction.A Load-use delay can be handled either statistically or dynamically. If the static resolution is ... Read More

Load and Stores are frequent operations, especially in RISC code. While executing RISC code we can expect to encounter about 25-35% load instructions and about 10% store instructions. Hence, it is one of big significance to execute load and store instructions effectively.It can summarize the subtasks which have to be performed during a load or store instructions as shown in the figure.Let us first consider a load instruction. Its execution begins with the determination of the effective memory address (EA) from where data is to be fetched. In this case, like RISC processors, this can be done in two steps: ... Read More

FX Pipelines can be implemented as either universal or dedicated FX units. Furthermore, a processor can incorporate either a single universal unit multiple universal units.Single Universal FX UnitsAll earlier and some current designs employ a single universal FX Pipeline, which is a single FX unit as shown in the figure. Here the adjective universal refers to the capability of executing all integers and Boolean operations of the processor. Besides the earlier pipelined processors of the 1980s, the i486, IBM Power1 (RS/6000), R (4000), HP 7100, DEC α 21064, PowerPC 601, and Power603 have a single universal FX pipeline and thus ... Read More

A logical layout of an FX pipeline consists, first of the specification of how many stages an FX pipeline has and what tasks are to be performed in these stages. The other key aspect of the design space is how FX pipelines are implemented. FX pipeline can be interpreted in both a broader and narrower sense.In the broader sense, it covers the full task of instruction fetch, decode, execute and if required writeback. In this case, it is usually also employed for the execution of L/S and branch instructions and is termed as master pipeline.In the narrower sense, an FX ... Read More

Performance in an unpipelined processor is characterized by the cycle time and the execution time of the instructions. In the case of pipelined execution, instruction processing is interleaved in the pipeline rather than performed sequentially as in non-pipelined processors. Therefore the concept of the execution time of instruction has no meaning, and the in-depth performance specification of a pipelined processor requires three different measures: the cycle time of the processor and the latency and repetition rate values of the instructions.The cycle time defines the time accessible for each stage to accomplish the important operations. The cycle time of the processor ... Read More

Pipelined instruction processing covers two key elements as the specification, or logical layout, and the implementation of instruction pipelines. The logical layout determines the tasks to be adept. It consists of the declaration of the pipelines to be executed and for each of the pipelines a detailed specification of the subtasks to be implemented and their execution sequence.In current processors, multiple pipelines are declared for each of the main instruction classes. There are generally independent pipelines for the processing of FX and logical data, known as the FX pipeline, for FP data, the FP pipeline, for loads and stores, the ... Read More

Pipelining defines the temporal overlapping of processing. Pipelines are emptiness greater than assembly lines in computing that can be used either for instruction processing or, in a more general method, for executing any complex operations. It can be used efficiently only for a sequence of the same task, much similar to assembly lines.A pipeline includes several stages, one for each subtask as shown in the figure. The stages are decoupled from each other by registers known as latches. As each clock style ends, the latches gate in their inputs and forward them into the associated stage where the needed operation ... Read More

Pipelining defines the temporal overlapping of processing. Pipelines are emptiness greater than assembly lines in computing that can be used either for instruction processing or, in a more general method, for executing any complex operations. It can be used efficiently only for a sequence of the same task, much similar to assembly lines.A basic pipeline processes a sequence of tasks, including instructions, as per the following principle of operation −Each task is subdivided into multiple successive subtasks as shown in the figure. For instance, the execution of register-register instructions can be broken down into instruction fetch, decode, execute, and writeback.A ... Read More

When instructions are handled in parallel, it is required to detect and resolve dependencies between instructions. It can generally discuss dependency detection and resolution as it associates to processor classes and the processing functions contained independently.An instruction is resource-dependent on an issued instruction if it needed a hardware resource that can be utilized by a previously issued instruction. If, for instance, only a single non-pipelined division unit is accessible, as in general in ILP-processors, thus in the code sequence the second division instruction is resource-dependent on the first one and cannot be implemented in parallel.Resource dependencies are constraints generated by ... Read More

Consider the following code sequence −mul r1, r2, r3; jz  zproc; sub r4, r7, r1; : zproc:load r1, x; :In this example, the real direction of implementation depends on the result of the multiplication. This represents that the instructions following a conditional branch are dependent on it. In a similar method, all conditional control instructions, including conditional branches, calls, skips, etc. promulgate dependencies on the logically subsequent instructions is known as control dependencies.The term general-purpose program stands for compilers, operating systems, or non-numeric application programs. The data indicates that that general-purpose program has a high percentage of branches, up to ... Read More