Computer Architecture Questions
The branch target buffer (BTB) is a cache-like structure used in computer architecture to improve the performance of branch instructions. It stores the target addresses of previously executed branch instructions, along with their corresponding branch conditions.
When a branch instruction is encountered, the BTB is checked to see if the branch instruction's address and condition match any entry in the buffer. If a match is found, the target address stored in the BTB is used to fetch the next instruction, avoiding the need for the processor to wait for the branch instruction to be resolved.
By predicting the target address of a branch instruction, the BTB helps to reduce the impact of branch penalties, which occur when the processor has to wait for the branch instruction to be resolved before fetching the next instruction. This improves the overall performance of the processor by reducing the number of pipeline stalls.
However, it is important to note that the BTB is not always accurate in predicting the target address, especially in cases where the branch condition changes frequently or the branch instruction is encountered for the first time. In such cases, the processor may have to discard the predicted target address and wait for the branch instruction to be resolved, resulting in a branch penalty.