"I spent three years building computers, and the more time I
spent doing so, the worse the computers I built got. You start
with a prebuilt, and end with an R720 full of Xeon Phis."
-Anonymous
I'm glad you asked, Xeon Phis are unique in that they are
CPU cores on a PCIe add in card, they're directly descended
from project Larrabee, Intel's attempt at building a
dedicated graphics card. Two generations of Phis were
launched, as well as a gen 2.5 refresh optimized for AI and
machine learning. The second generation of Xeon Phis
introduced socketed Xeon Phis that were a true x86 core,
instead of the K1om architecture that the first generation
of Xeon Phi cards utilized, which was not code compatible
with standard x86 CPUs.
Xeon Phis were most widely adopted in supercomputers and HPC
clusters, such as the Tianhe supercomputer, one of the most
powerful supercomputers in the world at the time, which used
Xeon Phi coprocessor cards for most of its performance.
They're easy to find! If you know where to look
First Generation Xeon Phi cards are easy to find on Ebay, such as the 31S1P, 5110P, 7110P. Good prices for these cards are usually under $50 shipped, and good listings pop up occasionally. If you use reddit, consider also checking out r/homelabsales
Bari
The One Who Knocks, Phinatics