Today’s processor is extremely fast that, they need to be constantly feed with the data from the RAM; otherwise, processor cycles will be spent idling.
The rate at which data transformation between RAM to processor is also know as effective bandwidth, or data throughput, measured by megabytes per seconds. This is depends upon bandwidth of the data bus, and the ability of the memory subsystem to fill up that bandwidth. The bandwidth is depends upon two factors; the width of the data bus, and the speed of the data bus or bus speed.
So you should have that RAM which matches the CPU requirement and perform the operation fast.