While they were quirky at the time (and I got some neat simulations out of them), they were a massive pain in the ass in every other way:

- Requires a motherboard that supports large PCIe BAR addressing, much more common now, not at release time (and good luck getting this working with multiple Xeon Phi coprocessors on a non-server motherboard) - You likely need enough host memory to cover each of the cards (so 8GB * number of cards) - You'll need to patch the Intel MPSS kernel driver to work with newer kernels - You'll need to patch the Intel MPSS tools to work on anything that isn't ~2015 RHEL - You'll want to buy the water cooling kit that alphacool made for them, it's the only way to keep temperatures and noise to a reasonable level

Solve all of those, and you get a (fairly cheap) coprocessor reasonably good at parallel yet branchy tasks. It's much easier to use the second generation of KNL (or third-generation KNM) which share the standard X86_64 ABI and can boot a modern Linux distro and you can use a normal toolchain).

Never found Knights Mill available anywhere. My understanding is that they were only available to integrators in the HPC space.