My recent forays in x86 segmentation (1 2) made me notice a trend in the evolution of x86: the decline of fine-grained memory protection, both across the move to 64-bit and indeed before that in the fast system calling features. These both partially hobbled the sophisticated segmentation system, which had been a hallmark of the architecture since the 286. The explanation is possibly Unix: the dominance of Unix and its preference for flat address spaces, rather than segmented ones, arguably inherited from the PDP-11 or indeed PDP-7, meant that “nobody wanted” a 64-bit version of the segmentation features.