SiFive announces high-performance U8-Series

Semiconductor specialist SiFive has announced the launch of its latest RISC-V-based core intellectual property (IP), and this time it's taking aim at the high-performance market: The SiFive U8-Series.

Building its products around the free and open source RISC-V instruction set architecture (ISA), SiFive's initial designs concentrated on offering alternatives to low-power microcontrollers. The launch of the HiFive Unleashed single-board computer back in February 2018 showed the company had visions of high-performance parts, however - visions which include, according to chief executive Naveed Sherwani, seeing RISC-V based commercial smartphones within three years and RISC-V based servers within five.

The SiFive U8-Series, then, is a step towards that goal. Still using the RISC-V ISA, the U8-Series comes in two flavours: The SiFive U84 and the SiFive U87, the latter offering vector processing functionality missing from the former. Compared to the company's previous generation, SiFive claims the U84 boosts performance by 3.1x - 2.3x of which is from an increase in instructions per cycle (IPC) while the part also includes a 1.4x increase in maximum operating frequency - while being able to fit in a 2.63mm² footprint with 2MB of L2 cache - or 0.28mm² if you drop the cache. That's competitive with Arm's popular Cortex-A72, the company claims, with the U84 boasting twice the area efficiency and 1.5x the performance-per-watt - based, it must be noted, on SiFive's own calculations.

SiFive is also pushing the scalability and modularity of its IP: As well as being able to use the IP on a variety of process nodes, the U8-Series will allow customers to specify how the out-of-order pipeline operates - either accepting the 12-stage pipeline as-is or adjusting the depth, issue queue count, and other options to suit a particular workload. The company also offers a Mix+Match system, similar to Arm's big.LITTLE, where a 'core complex' can be made up of cores from various SiFive IP families - all of which can include custom instructions.

More information on the new cores, for which SiFive has not yet announced any custom wins, is available on the SiFive blog.