Intel Launches Knights Landing-based Xeon Phi AIBs
Subject: Processors | November 18, 2015 - 07:34 AM | Scott Michaud
Tagged: Xeon Phi, knights landing, Intel
The add-in board version of the Xeon Phi has just launched, which Intel aims at supercomputing audiences. They also announced that this product will be available as a socketed processor that is embedded in, as PC World states, “a limited number of workstations” by the first half of next year. The interesting part about these processors is that they combine a GPU-like architecture with the x86 instruction set.
Image Credit: Intel (Developer Zone)
In the case of next year's socketed Knights Landing CPUs, you can even boot your OS with it (and no other processor installed). It will probably be a little like running a 72-core Atom-based netbook.
To make it a little more clear, Knights Landing is a 72-core, 512-bit processor. You might wonder how that can compete against a modern GPU, which has thousands of cores, but those are not really cores in the CPU sense. GPUs crunch massive amounts of calculations by essentially tying several cores together, and doing other tricks to minimize die area per effective instruction. NVIDIA ties 32 instructions together and pushes them down the silicon. As long as they don't diverge, you can get 32 independent computations for very little die area. AMD packs 64 together.
Knight's Landing does the same. The 512-bit registers can hold 16 single-precision (32-bit) values and operate on them simultaneously.
16 times 72 is 1152. All of a sudden, we're in shader-count territory. This is one of the reasons why they can achieve such high performance with “only” 72 cores, compared to the “thousands” that are present on GPUs. They're actually on a similar scale, just counted differently.
Update: (November 18th @ 1:51 pm EST) I just realized that, while I kept saying "one of the reasons", I never elaborated on the other points. Knights Landing also has four threads per core. So that "72 core" is actually "288 thread", with 512-bit registers that can perform sixteen 32-bit SIMD instructions simultaneously. While hyperthreading is not known to be 100% efficient, you could consider Knights Landing to be a GPU with 4608 shader units. Again, it's not the best way to count it, but it could sort-of work.
So in terms of raw performance, Knights Landing can crunch about 8 TeraFLOPs of single-precision performance or around 3 TeraFLOPs of double-precision, 64-bit performance. This is around 30% faster than the Titan X in single precision, and around twice the performance of Titan Black in double precision. NVIDIA basically removed the FP64 compute units from Maxwell / Titan X, so Knight's Landing is about 16x faster, but that's not really a fair comparison. NVIDIA recommends Kepler for double-precision workloads.
So interestingly, Knights Landing would be a top-tier graphics card (in terms of shading performance) if it was compatible with typical graphics APIs. Of course, it's not, and it will be priced way higher than, for instance, the AMD Radeon Fury X. Knight's Landing isn't available on Intel ARK yet, but previous models are in the $2000 - $4000 range.