The Kernel Hacker's Bookshelf: Ultimate Physical Limits of Computation

In the original article, the author makes it much more clear that we are assuming nothing
about what the technology of computers in the future looks like.  In particular, we're not
assuming that the storage of the computer is compartmentalized into a small box containing
spinning rust-covered disks. :) All the calculations are based solely on the mass and volume
of the computer, with no assumptions about distribution.