Other things like cache coherency, number and type of cores, other things running on the system, compression or reduction based on properties of the data all have an effect on what is possible. Not to mention weird things like some specialised FPGA, GPU, network card, or even SSD that might have DMA'd the memory. Various bus types depending on the cpus can also have a massive effect - not to mention memory access patterns your code might use. What about the OS level abilities that you're allowed to use? Is ring 0, or setting the affinity of processes, or enabling Turbo mode allowed? Maybe you don't give a shit about the data structure at all, and are just searching for a word with hyper-optimised grep will win. Then taking advantage of that, you can cheat and get something even faster. As you can see, even getting into the level of detail you mention, there is still a shit-load of extra details that might be needed to take full advantage of the hardware.

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