Xeon Phi

Xeon Phi
Name	Xeon Phi
Developer	Intel
Type	Manycore coprocessor
Released	2012
Discontinued	2020
Predecessor	Larrabee
Successor	Data Center GPU Max Series

Xeon Phi. It was a family of manycore processors and coprocessors from Intel, designed for high-performance computing and scientific computing workloads. The architecture originated from the earlier Larrabee project and was positioned to compete with Nvidia's Tesla and AMD's FireStream products. Production of new products was discontinued in 2020, with its architectural concepts influencing subsequent Intel Xe GPU designs.

Overview

The product line was launched as a strategic effort by Intel to capture a significant share of the supercomputer and technical computing market. Initial products were offered in a PCI Express card form factor, functioning as a coprocessor alongside a conventional Xeon central processing unit. This approach was similar to that of Nvidia with its CUDA platform, aiming to accelerate parallel computing tasks. The family was later expanded to include self-booting, socketed processors that could operate as the primary CPU in a server.

Architecture

The core design was based on an in-order execution x86 architecture, featuring a large number of relatively simple Pentium-derived cores. These cores supported 64-bit computing via the x86-64 instruction set and included a 512-bit wide SIMD unit, known as AVX-512. A key innovation was the use of a high-speed, bidirectional ring bus interconnect to link the cores with a shared, coherent L2 cache and GDDR5 memory controllers. This memory architecture provided high memory bandwidth, critical for computational science applications.

Product Generations

The first generation, codenamed Knights Corner, was introduced in 2012 and manufactured on a 22 nm process. It featured up to 61 cores and was exclusively a PCI Express coprocessor. The second generation, Knights Landing, launched in 2016, moved to a 14 nm process and was available both as a coprocessor and a standalone CPU with integrated Omni-Path fabric support. The final generation, Knights Mill, was a specialized variant of Knights Landing optimized for deep learning and released in 2017, featuring enhanced floating-point capabilities.

Programming Models

A primary goal was to enable programming in familiar languages, leveraging its x86 foundation. The primary parallel programming models were OpenMP and Intel MPI for distributed memory systems. Intel also provided low-level APIs through its Intel C++ Compiler and libraries like the Intel Math Kernel Library. While it supported a variant of the OpenCL standard, the most significant proprietary alternative was Nvidia's CUDA, which dominated the GPGPU market. Efforts to create a common standard led to support for the SYCL programming model.

Applications and Performance

The processors found significant use in large-scale supercomputer deployments, most notably in the Tianhe-2 system at the National Supercomputing Center in Guangzhou, which used thousands of Knights Corner coprocessors. They were applied to problems in computational fluid dynamics, molecular modeling, and climate research. In benchmarks like the LINPACK used for the TOP500 list, systems equipped with these processors demonstrated high floating-point performance. However, for many artificial intelligence workloads, the architecture was often outperformed by Nvidia's Volta and subsequent GPU architectures.

Discontinuation and Legacy

Intel officially announced the discontinuation of the product line in June 2020, ceasing production of Knights Landing and Knights Mill products. The company shifted its strategic focus towards discrete GPUs for high-performance computing, culminating in the Intel Data Center GPU Max Series. The architectural experience, particularly in manycore design and the AVX-512 instruction set, directly informed the development of Intel Xe GPU architectures. Furthermore, technologies like the Omni-Path fabric continued in other Intel enterprise products.

Category:Intel microprocessors Category:High-performance computing Category:Computer-related introductions in 2012 Category:Discontinued Intel products