- what is the speed of your data source?
You may find that the speed of your data source is the limiting factor on modern CPUs. Unless you can fit 6.5 TB into RAM it is going to have to be streamed from somewhere (and even if you can, it’s going to have to be loaded from somewhere into RAM still?) and I doubt you’ll have more than a few GB/sec of bandwidth to load it from?
You might not need the “fastest” CPU for sha256 if you’re bandwidth limited anyway.