Via Andrew Back at AB Open via Hackaday – While it’s clear that the most significant opportunities for RISC-V will be in democratising custom silicon for accelerating specific tasks and enabling new applications — and it’s already driving a renaissance in IoT and edge processing. But, when can I have a RISC-V PC? The answer is, right now.
The SiFive HiFive Unleashed board provides a 64-bit quad-core RISC-V processor built in TSMC 28nm process, plus 8GB DDR4 ECC memory, and as such offers decent performance. Along with a console UART this features gigabit Ethernet and while there is no on-board USB or PCIe, it does have an FPGA Mezzanine Connector (FMC). This allows connection to an FPGA development board and together these provide an excellent combination of performance and flexibility.
The HiFive Unleashed has a companion Expansion Board from Microsemi which features a mating connector, Polarfire FPGA and peripheral I/O. Currently, a bitstream is provided for configuring the FPGA to implement a ChipLink interface towards the RISC-V processor and a PCIe root complex, in turn connected to a PCIe switch ASIC. There is one 16x connector, another 1x and an M.2 slot, for a total of three PCIe slots.
The Expansion Board also has a SATA interface, along with HDMI and USB connectors which could potentially be used with a new FPGA bitstream. The quickest way to complete our PC was to simply add a PCIe USB 3.0 controller and a graphics card which had open source drivers. We decided to fit both M.2 PCIe NVMe and SATA SSD storage for good measure.
The result is a RISC-V powered system that can be used as a desktop computer and thanks to the efforts of Atish Patra at Western Digital, installing Fedora Linux is a breeze. This is obviously not exactly commodity hardware, but it does show that the ingredients are there and the combination provides a powerful development platform for anyone who might want to prototype a RISC-V PC — or indeed a vast array of other applications which stand to benefit from the open ISA.