Fast simulation of digital circuits is crucial to build modern chips. But RTL (Register-Transfer-Level) simulators are slow, as they cannot exploit multicores well. Slow simulation lengthens chip design time and makes bugs more frequent.

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.

With Moore's Law coming to an end, hardware specialization and systems on chips are providing new opportunities for continuing performance scaling while reducing the energy cost of computation. However, the current hardware design methodologies require significant engineering efforts and domain expertise, making the design process unscalable. More importantly, hardware specialization presents a unique challenge for a much tighter software and hardware co-design environment to exploit domain-specific optimizations and design efficiency. In this work, we introduce Cash, a single-source hardware-software co-design framework for rapid SoC prototyping and accelerators research. Cash leverages the unique efficiency and generative attributes of Modern C++ to provide a unified development environment, aiming at closing the architecture research methodology gap. The Cash framework introduces new co-design programming abstractions that enable seamless integration with existing software from architecture research simulators to high-level synthesis.