Vortex: Extending the RISC-V ISA for GPGPU and 3D-GraphicsResearch

TL;DR

This paper introduces Vortex, an open-source GPU built on an extended RISC-V ISA, supporting GPGPU and graphics, implemented on FPGA with scalable cores and broad application potential.

Contribution

It proposes a minimal ISA extension to RISC-V for GPGPU and graphics, enabling an open-source GPU ecosystem with a complete FPGA implementation.

Findings

Vortex supports OpenCL and OpenGL on FPGA.

Scales up to 32 cores with 25.6 GFlops peak performance.

Minimal ISA changes facilitate ecosystem sustainability.

Abstract

The importance of open-source hardware and software has been increasing. However, despite GPUs being one of the more popular accelerators across various applications, there is very little open-source GPU infrastructure in the public domain. We argue that one of the reasons for the lack of open-source infrastructure for GPUs is rooted in the complexity of their ISA and software stacks.In this work, we first propose an ISA extension to RISC-V that supports GPGPUs and graphics. The main goal of the ISA extension proposal is to minimize the ISA changes so that the corresponding changes to the open-source ecosystem are also minimal, which makes for a sustainable development ecosystem. To demonstrate the feasibility of the minimally extended RISC-V ISA, we implemented the complete software and hardware stacks of Vortex on FPGA. Vortex is a PCIe-based soft GPU that supports OpenCL and OpenGL.Vortex can be used in a variety of applications, including machine learning, graph analytics, and graphics rendering. Vortex can scale up to 32 cores on an Altera Stratix 10 FPGA, delivering a peak performance of 25.6 GFlops at 200 Mhz.