@cliffrowley Ahh apologies! You were making the previous fragile check (OS  X  >  SL) more solid by changing it be explicit in it's requirements (OS X  >= Lion + SSSE3 support)

I completely agree, and outside of this SSSE3 issue your logic is totally sound (and an improvement on how it was).

I misunderstood and thought you were hoping this conditional would lead to a successful compilation by 2013 machines. We know this won't work as clearly the presence of SSSE3 support is not the issue here, it's something seemingly Haswell specific. We both on the same page now? ;)

Here's the output: https://gist.github.com/jabooth/7242323

    machdep.cpu.extmodel: 4

looks useful (Haswell is the 4th generation Core architecture)