SiFive BigSky SF-2U870: First Rackable 2U RISC-V Datacenter Server

Overview

On August 24, 2026, at an event coinciding with Hot Chips, SiFive announced the BigSky SF-2U870 datacenter development platform — the first enterprise-grade, rackable 2U RISC-V server. It is explicitly positioned as a turnkey development vehicle for hyperscalers, software vendors, and SoC teams to port, tune, and validate server workloads on RISC-V before deploying production silicon.

BigSky is not a reference board or evaluation kit. It is a full server platform with:

• 32 SiFive P870-D RISC-V cores at 2.0 GHz
• 256 GB DDR5-5600 system memory
• 4x PCIe Gen5 x16 slots (64 lanes) plus PCIe Gen3 x4
• 2x 7.68 TB U.2 NVMe SSD
• 10/25 Gb OCP 3.0 NIC
• Out-of-the-box Ubuntu 26.04 LTS and Red Hat RHEL 10 support
• Full RVA23 compliance, enabling standard enterprise software ports

SiFive also confirmed it is working with NVIDIA to port CUDA to SiFive-based RISC-V hardware and to integrate NVLink Fusion into future platforms — and that CUDA is already running on the BigSky platform as a head node for NVIDIA GPU-accelerated LLM workloads.

Key Specifications

Vendor	SiFive
Product	BigSky SF-2U870
Form Factor	2U rackmount server
Announced	August 24, 2026
CPU	32x SiFive P870-D RISC-V cores @ 2.0 GHz
ISA Profile	RVA23 (full compliance)
Memory	256 GB DDR5-5600
PCIe	4x PCIe Gen5 x16 (64 lanes) + PCIe Gen3 x4
Storage	2x 7.68 TB U.2 NVMe SSD
Networking	10/25 Gb OCP 3.0 NIC
Operating Systems	Canonical Ubuntu 26.04 LTS, Red Hat RHEL 10
GPU Ecosystem	NVIDIA CUDA ported; NVLink Fusion roadmap
Target Use	Software porting, workload tuning, system validation
Availability	Limited quantities shipping now (contact SiFive sales)

The P870-D Core

The P870-D is SiFive's latest data-center-class RISC-V CPU. It is a derivative of the Performance P870 family, optimized for server workloads with deep caches, enhanced RAS (reliability, availability, serviceability) features, and full RVA23 support. At 32 cores and 2.0 GHz in the BigSky platform, it delivers a substantial amount of integer and vector throughput in a single socket.

RVA23 compliance is critical because it removes the need for custom software ports. Standard enterprise Linux distributions, container runtimes, and compilers can run without vendor-specific patches. This is the same profile that NVIDIA now requires for CUDA on RISC-V.

Why a Development Server, Not a Production Server

SiFive is clear that BigSky is a development platform, not a production server SKU. Its purpose is to close the software gap that has historically slowed RISC-V adoption in the datacenter:

• Software porting: Give enterprise ISVs and open-source projects real hardware to compile, test, and optimize on.
• Workload tuning: Validate compiler flags, vectorization, threading models, and memory behavior under real server conditions.
• System validation: Exercise PCIe, NIC, storage, and GPU attach points at production-like scale.

By providing a 2U rackable form factor with standard DDR5, PCIe Gen5, NVMe, and OCP NIC, BigSky fits into existing datacenter racks and operational workflows. This lowers the friction for teams that want to evaluate RISC-V without building custom hardware.

NVIDIA CUDA and NVLink Fusion Integration

The most strategically significant announcement alongside BigSky is SiFive's collaboration with NVIDIA. Key points:

• CUDA on RISC-V: NVIDIA is porting CUDA to run on SiFive RISC-V CPUs. SiFive has already demonstrated CUDA running on BigSky, with the RISC-V host acting as the head node for NVIDIA GPU-accelerated LLM workloads.
• RVA23 baseline: NVIDIA's RISC-V CUDA support requires RVA23 CPU profile, RISC-V Server SoC specification, and RISC-V Server Platform specification — including UEFI/ACPI boot, PCIe coherency, and peer-to-peer DMA.
• NVLink Fusion: SiFive will integrate NVIDIA's NVLink Fusion C2C interconnect in future datacenter chips, enabling cache-coherent CPU-GPU links with up to ~5x the bandwidth of PCIe for AI inference pipelines.

This positions RISC-V as a third-tier host architecture in NVIDIA's ecosystem, alongside x86 and ARM, but strictly for server-grade silicon. Consumer RISC-V boards do not meet the requirements and will not run CUDA.

Quick Start: Check RVA23 Compliance

If you are targeting BigSky or any other CUDA-capable RISC-V platform, the first step is confirming the CPU implements the RVA23 profile. On a running Linux system, inspect the ISA string:

# Read the RISC-V ISA extensions exposed by the kernel
cat /proc/cpuinfo | grep isa

# Typical RVA23-capable output includes:
# rv64imafdcvh_zicbom_zicboz_zicsr_zifencei_zihintpause
# _zba_zbb_zbs_zkn_zks_svpbmt_svinval_svnapot_sstc

# Check for hypervisor (H) extension — required for server virtualization
riscv64-linux-gnu-readelf -A /proc/self/exe | grep Tag_RISCV_arch

For CUDA specifically, the platform must also expose PCIe coherency and peer-to-peer transfer capabilities. These are platform-level features, not CPU ISA features, and are documented in the RISC-V Server Platform specification.

Comparison With Other RISC-V Server Platforms

Parameter	SiFive BigSky SF-2U870	Milk-V Pioneer	SpacemiT K1 MUSE Shelf
Form Factor	2U rackmount	Micro-ATX workstation	1U / tower server
CPU	32x P870-D @ 2.0 GHz	4x SG2042 @ 2.0 GHz	8x X60 @ 1.6 GHz
ISA Profile	RVA23	RV64GC	RV64GC + RVV 1.0
Memory	256 GB DDR5-5600	Up to 128 GB DDR4	Up to 64 GB LPDDR4X
PCIe	Gen5 x64 lanes	Gen3 x24 lanes	Gen2
Target	Hyperscaler / enterprise validation	Developer workstation	Edge / gateway
GPU/CUDA	CUDA ported, NVLink Fusion roadmap	No	No

BigSky sits well above existing RISC-V server hardware in memory capacity, PCIe bandwidth, and target market. It is the first platform explicitly aimed at the same buyers who evaluate Intel Xeon, AMD EPYC, and ARM Neoverse servers.

What This Means for RISC-V

• Datacenter software gap is closing: A real rackable server with Ubuntu and RHEL support gives software vendors a concrete target.
• Hyperscaler engagement: SiFive states that lead customers — including hyperscalers and major SoC hardware leaders — are already running workloads on deployed BigSky systems.
• NVIDIA ecosystem entry: CUDA and NVLink Fusion validation put RISC-V on the map for AI infrastructure, even if production deployments are still 2027+.
• Supply-chain diversification: For operators seeking alternatives to x86 and ARM at the rack level, BigSky is the first credible RISC-V development vehicle.

Limitations and Open Questions

• Availability: SiFive says the platform is in "limited quantities" and demand is outpacing supply. It is not yet a general-purpose product.
• Pricing: No public pricing has been announced.
• Benchmarks: Third-party performance numbers under SPEC, database, and AI inference workloads are not yet available.
• CUDA timeline: While CUDA runs on BigSky today, broad software qualification and production GPU deployments will take time.
• NVLink Fusion silicon: Chips with integrated NVLink Fusion are not expected before 2027.

Official Resources

• SiFive BigSky SF-2U870 Press Release
• SiFive Performance P800 Series Cores
• SiFive + NVIDIA NVLink Fusion Announcement
• RISC-V Specifications (including RVA23)
• Ubuntu for RISC-V

Bottom Line

SiFive BigSky is the most credible RISC-V datacenter platform announced to date. It does not instantly make RISC-V a mainstream server option, but it removes the "no hardware to develop on" excuse for enterprise software vendors and hyperscalers. Combined with NVIDIA CUDA and NVLink Fusion support, it gives the ecosystem a clear roadmap for RISC-V in AI and cloud infrastructure.