SIMD is Single instruction multiple data it is microprocessor concept use to increase the performance execution. Processor uses special registers called MMX for this. I don't have idea about MIMD. Cache is used to increase performance too. Their are common two cache 1. primary cache that is built on the processor and fastest cache. 2. secondary cache it is attached to processor by a high speed bus and it is also fast but not as primary cache. Cache are created from static ram, a type of memory.