Bosschere. A technique for high-bandwidth and deterministic low latency load/store accesses to multiple cache banks

One of the problems in future processors will be the resource conflicts caused by several load/store units competing to access the same cache bank. The traditional approach for handling this case is by introducing buffers combined with a cross-bar. This approach suffers from (i) the nondeterministic latency of a load/store and (ii) the extra latency caused by the cross-bar and the buffer management. A deterministic latency is of the utmost importance for the forwarding mechanism of out-of-order processors because it enables back-to-back operation of instructions. We propose a technique by which we eliminate the buffers and crossbars from the critical path of the load/store execution. This results in both, a low and a deterministic latency. Our solution consists of predicting which bank is to be accessed. Only in the case of a wrong prediction a penalty results. 1