Tensor Slices: FPGA Building Blocks For The Deep Learning Era

Abstract

FPGAs are well-suited for accelerating deep learning (DL) applications owing to the rapidly changing algorithms, network architectures and computation requirements in this field. However, the generic building blocks available on traditional FPGAs limit the acceleration that can be achieved. Many modifications to FPGA architecture have been proposed and deployed including adding specialized artificial intelligence (AI) processing engines, adding support for smaller precision math like 8-bit fixed point and IEEE half-precision (fp16) in DSP slices, adding shadow multipliers in logic blocks, etc. In this paper, we describe replacing a portion of the FPGA’s programmable logic area with Tensor Slices. These slices have a systolic array of processing elements at their heart that support multiple tensor operations, multiple dynamically-selectable precisions and can be dynamically fractured into individual multipliers and MACs (multiply-and-accumulate). These slices have a local crossbar at the inputs that helps with easing the routing pressure caused by a large block on the FPGA. Adding these DL-specific coarse-grained hard blocks to FPGAs increases their compute density and makes them even better hardware accelerators for DL applications, while still keeping the vast majority of the real estate on the FPGA programmable at fine-grain.