Comment by doctor_phil

When we are talking about galactic algorithms we have long since left the realm of things that might fit on one computer. Some of these algorithms are only starting to become faster on n so large that we have trouble fitting the data in this solar system. At those scales the distinction between the type of RAM is irrelevant. At that point "how long to read memory address X" is pretty much the same as "how long does light take to reach X" which is pretty much "how far to X" which scales with a cube root. (Well, probably a square root if we look at physical limits for weird reasons)