This scheme employs a more cache, known as the branch target address cache (BTAC), for speeding up access to branch targets as shown in the figure. The BTAC includes a group of currently used branch addresses and branch target addresses and is accessed relatively.When the actual instruction fetch address is ... Read More

This scheme is the common approach to accessing branch targets. First, the branch target address (BTA) is evaluated either by the pipeline or by a dedicated adder. Thus, the matching branch target instruction (BTI) is fetched. In current processors, this defines access to the I-cache, whereas in initial pipelined processors ... Read More

There are two basic tasks to be implemented the discard the results of the speculative execution and resume execution of the alternative, that is, the true path as shown in the figure.When there is higher than one pending conditional branch, the corresponding alternative path should be chosen and followed. In ... Read More

A processor extends to execute instructions speculatively until the condition is resolved. The time interval between the beginning of the conditional execution and the resolution of the equivalent condition can change significantly. The condition is resolved the immediately following cycle.This appears when the specified condition defines the result of a ... Read More

History bits are used to record branch history. Processors employ one of the four different schemes to implement history bits as shown in the figure. In the most straightforward scheme history bits are placed in the I-cache.For instance, the α processors provide one (21064) or two (21064A) history bits in ... Read More

There are two different approaches for expressing the history of branches as shown in the figure. In the explicit dynamic technique, branch history is explicitly stated in the form of history bits. The actual implementation of this technique using one, two, or three bits for expressing the history. The second ... Read More

In a static prediction technique, the branch is ‘always taken’ or the branch is ‘always not-taken’ approaches. It can make static predictions by investigating particular attributes of the object code. In actual implementation, static predictions are either opcode-based, displacement-based, or based on a hint delivered by the compiler, as shown ... Read More

In a fixed prediction a similar guess is continually made, either ‘always taken’ or ‘always not-taken’ approaches.‘Always not-taken approach’ − The ‘always not taken’ approach (or ‘not taken’ approach for short) has the following typical processing scheme are as follows −It can detect an unresolved conditional branch and guess it ... Read More

The branch prediction scheme used in a processor has a central impact on its execution. Therefore, some effort has been placed into promoting an effective scheme.A prediction can be a fixed or a true prediction. In a fixed prediction the same guess is continually made, either ‘taken’ or ‘not-taken’. This ... Read More

A conditional branch cannot be computed earlier than the referenced conditional is known. For instance, if the specified condition defines the sign of the outcome of the previous instruction, the precondition of the computation is that the previous instruction has been performed.Until the referenced condition will become known, the conditional ... Read More