Or maybe 3x9 if you are doing wild random accesses in big area, or even worse in huge area if your TLB and then caches start to not hold enough and you effectiv

Or maybe 3x9 if you are doing wild random accesses in big area, or even worse in huge area if your TLB and then caches start to not hold enough and you effectively need to do multiple accesses for each single ones, but you are right: DRAM is faster. However, caching Optane with real DRAM seems a really good idea (or maybe using Optane as swap could be useful too)