All true, to add to this there's all sorts of other caveats on modern processors. E.g. it may be slower to access any of L1-3 or RAM depending on what processor

All true, to add to this there's all sorts of other caveats on modern processors. E.g. it may be slower to access any of L1-3 or RAM depending on what processor core you're on. This is because even though your program can transparently access all that memory, the underlying machine is implemented in terms of memory areas and it can be costly to "jump across" a memory boundary[1][2][3]. 1. https://linux.die.net/man/8/numactl https://linux.die.net/man/8/numactl 2. https://linux.die.net/man/1/taskset https://linux.die.net/man/1/taskset 3. http://iopscience.iop.org/article/10.1088/1742-6596/664/9/092010/pdf http://iopscience.iop.org/article/10.1088/1742-6596/664/9/09...