On August 24, 2026, SiFive announced BigSky SF-2U870, a 2U rack-mounted datacenter development machine equipped with 32 RISC-V CPU cores. The goal isn't to sell mass volumes of a finished commercial server, but to give hyperscalers and software companies real hardware on which they can carry out RISC-V porting, optimization, and system validation. The premise behind RISC-V servers has advanced a step—from the stage of merely evaluating CPU IP to the stage of continuously validating Linux and CUDA in a rack. That said, the evidence needed to judge actual performance and supply capability remains thin.
32 Cores in a 2U Chassis: From Development Board to Rack Hardware
BigSky carries 32 units of the P870-D, fabricated on TSMC's N6 process, and according to SiFive's current announcement, they run at 2.0GHz. Memory consists of 256GB of DDR5-5600, and expansion I/O includes four PCIe Gen5 x16 slots for a total of 64 lanes. It also includes PCIe Gen3 x4 and an OCP 3.0 NIC supporting 10/25Gb, plus room for double-wide GPUs. Storage is listed as two 7.68TB U.2 NVMe SSDs.
The previous HiFive Premier P550 was a Mini-DTX development board meant for trying out RISC-V Linux on a desktop. BigSky extends that same development purpose into the I/O and GPU connectivity needed in a rack.
| Item | BigSky SF-2U870 | HiFive Premier P550 |
|---|---|---|
| Form factor | 19-inch, 2U rack unit | Mini-DTX board |
| CPU | P870-D ×32, officially announced at 2.0GHz | P550 ×4, 1.4GHz |
| Memory | 256GB DDR5-5600 | 16GB or 32GB LPDDR5 |
| PCIe | Gen5 x16 ×4 plus Gen3 x4 | Gen3 x4 |
| Default OS | Ubuntu 26.04, with RHEL 10 stated by SiFive | Ubuntu 24.04 |
Core count is 8 times greater, and memory capacity is 8 or 16 times greater. But that doesn't mean system performance scales by the same ratio. SiFive has not disclosed BigSky's power consumption, memory channel count, or cache capacity. There's no pricing or published benchmark either, so it's not yet possible to compare performance or operating cost against mass-produced x86 or Arm servers.
Moreover, SiFive's product page contains inconsistent specifications. The main spec sheet and the announcement text state 2.0GHz and two 7.68TB SSDs, while another section on the same page lists 2.2GHz and 3.84TB. For now, it seems reasonable to go with the matching figures of 2.0GHz and two 7.68TB drives, but SiFive needs to issue a correction before this can inform any purchasing decision.
Availability also differs from a standard retail launch. SiFive describes it as "currently available," but production is limited in quantity, and the target is strategic development projects. The explanation that demand exceeds supply comes without any unit numbers, and pricing requires contacting sales. SiFive says that leading hyperscalers, software companies, and major SoC firms are already running workloads on delivered units, but customer names and validation results remain undisclosed.
What RVA23 Delivers—and What It Doesn't
The technical milestone represented by BigSky is the arrival of rack-based hardware compliant with RVA23. RVA23 is a common instruction set baseline for 64-bit application processors, including vector operations and hypervisor-related features. It reduces the burden on OS, compiler, and application developers who would otherwise need to track which instructions are present on a vendor-by-vendor basis. This is also why Canonical adopted RVA23 as the baseline starting with Ubuntu 25.10.
However, RVA23 is an ISA profile, not a conformance standard for a complete server. Server Platform v1.0, published by RISC-V International in May 2026, specifies everything from RVA23-compliant cores and SoCs to peripherals, UEFI/ACPI, and BMC management and security. SiFive has not stated that BigSky complies with Server Platform v1.0.
This distinction matters for datacenter operations. Software being able to use the same instructions is a separate matter from whether remote management, fault logging, and firmware updates can be integrated into existing operational infrastructure. BigSky has made significant progress on the former, but the scope of its compliance with the latter has not yet been disclosed.
The Gap Between Ubuntu 26.04 and RHEL 10
SiFive lists Ubuntu 26.04 LTS and RHEL 10 as OSes that work "out of the box." On the Ubuntu side, there is publicly available information that aligns with this claim. Canonical states that RISC-V builds of Ubuntu starting with 25.10 use RVA23 as the minimum baseline, and that Ubuntu 26.04 LTS receives standard 5-year support, extendable to up to 15 years under Ubuntu Pro. BigSky's RVA23 compliance satisfies the condition needed to run on this standard binary environment.
RHEL requires more careful reading. SiFive's announcement includes a Red Hat technology strategist discussing RHEL 10 running on BigSky, while Red Hat's own public documentation, updated in June 2026, still labels the RISC-V build of RHEL 10.2 as a Developer Preview, with the HiFive Premier P550 remaining the target hardware. Other boards may have boot examples, but these are described as experimental and requiring adjustments.
So while getting RHEL 10 to boot on BigSky is progress, it doesn't mean Red Hat has certified a general-availability release or extended production support. It will be necessary to check whether Red Hat updates its list of supported hardware, known limitations, and support terms following SiFive's announcement.
Running CUDA, and NVLink Fusion on the Horizon
For AI workloads, SiFive announced that it ran CUDA on a P870-D-equipped BigSky system. This does not mean the RISC-V CPU is performing GPU computation itself. Rather, it means that the CUDA software stack—used to hand off jobs to NVIDIA GPUs and control LLM training and inference—ran on RISC-V, with BigSky serving as the host and head node.
The current BigSky supports double-wide GPUs via PCIe Gen5 x16. However, the NVLink Fusion integration that SiFive is pursuing with NVIDIA is intended for future platforms. NVLink Fusion is a planned high-bandwidth, coherent interconnect linking CPUs and GPUs, and there's no indication that it's already implemented in this 2U unit. The CUDA version and GPU used are unknown. Neither the drivers nor the LLMs tested have been disclosed, and performance and stability figures haven't been published either. "It ran" cannot be extended to mean it's production-ready.
BigSky's 32 cores are not described as a mass-production configuration that previews a future large-scale RISC-V CPU. This hardware should instead be seen as a reference machine meant to cultivate software and operational procedures ahead of time.
Before Performance Charts, an Entry Point for Porting and CI
SiFive is not a company that sells finished CPUs in bulk; it supplies CPU IP that customers integrate into their own SoCs. The purpose of distributing BigSky isn't to compete on unit sales of a proprietary 2U server. Rather, it's to let OSes and drivers run on real hardware while customers design their future RISC-V SoCs—buying time to fix containers, databases, and AI software, and get them onto continuous integration pipelines.
Whether this development machine succeeds will be determined not by the 32-core number, but by whether the ported software makes it upstream and whether the same binaries run on RVA23 machines from other vendors. General availability needs to arrive first, along with pricing, power consumption figures, and third-party benchmarks. Once compliance with Server Platform v1.0 and Red Hat's support status are also in place, BigSky will transform from a test rig that put RISC-V into a rack into a bridge toward mass-produced datacenter SoCs.