The SiFive Freedom U540 is the first chip with the open 64-bit RISC-V architecture. So, it is very special for developers. Also, its four RV64GC cores run on Linux. The 64-bit versions of the open RISC-V microarchitecture could previously only be used in FPGA chips. SiFive announces the Freedom U540 RV64GC processor with four U54 cores, 2MB L2 cache, up to 1.5GHz clock speed and DDR4 memory controller. The developer board HiFive Unleashed with a Freedom U540, 8 GB of RAM and Gigabit Ethernet can be pre-ordered at Crowdsupply for 999 US dollars SiFive wants to deliver it from June. For 1250 US dollars there are 60 boards already in March.
The Freedom U540 28nm chip is a system-on-chip (SoC) that includes the U54 cores as well as an E51 as a management core (RV64IMAC), as well as controllers for Gigabit Ethernet, SD cards, and interfaces such as SPI and I²C.
PCIe, SATA or even USB are missing, however; they can be connected via ChipLink, for example with the help of an FPGA chip. SiFive cooperates with MicroSemi at ChipLink, whose PolarFire FPGAs are ChipLink-compatible.
SiFive HiFive Unleashed: Developer board with Freedom U540 and 8 GB DDR4 SDRAM
Image: SiFive
SiFive HiFive Unleashed
The HiFive Unleashed also has a 32 MByte SPI flash chip for firmware and a MicroSD card reader. An FTDI FT2232H provides a USB port for programming.
The recently released Linux kernel 4.15 supports RISC-V. The Arduino-compatible developer board SiFive HiFive1 with the 32-bit SiFive E310. However, runs about under the now maintained by Amazon FreeRTOS .