I have a question, for 256GB memory configuration, how much the difference in latency time between 16 x 16GB 1600 RDIMM stick of memory and 16 x 16GB 1866 RDIMM stick of memory when a heavy loaded? I need a specific percentage, thank you!
I don't think anyone can provide a percentage because there are a number of factors, like how the memory is exercised, that will determine that.
That said, my personal experience is that you'll never see a difference using real-life workloads unless you're doing some VERY specific benchmarking. So I'd buy what's more economical. At the end of the day, all applications read/write to disk and 1ms difference in storage latency will mask any potential gain from the faster memory.