ASRock Rack 4U16X-GNR2 Makes Blackwell Ultra AI Servers Feel Real

As of Sunday, August 9, 2026, the ASRock Rack 4U16X-GNR2 is one of the clearer examples of what a current high-density Blackwell Ultra AI server looks like outside of slide decks. ServeTheHome published its hands-on coverage on July 27, 2026, showing a 4U NVIDIA HGX B300 system built around two Intel Xeon 6 Granite Rapids processors, eight NVIDIA Blackwell Ultra GPUs, onboard NVLink, and liquid cooling. The interesting part is not just that it is powerful; it is how much supporting infrastructure has to fit around the accelerators. This is a server where cooling loops, front-panel networking, redundant power, NVMe storage, and service access are all part of the story. (servethehome.com)

The tested configuration used Intel Xeon 6700P-class processors, with ServeTheHome specifically discussing a dual-socket, dual 64-core Xeon 6767P setup in its performance section. ASRock Rack’s design also centers on the NVIDIA HGX B300 platform, which NVIDIA describes as an eight-GPU Blackwell Ultra HGX configuration. NVIDIA’s HGX AI Factory documentation lists 288GB of HBM3e per B300 GPU, which puts an eight-GPU HGX B300 system at roughly 2.3TB of aggregate GPU memory. NVIDIA also describes HGX B300 as using fifth-generation NVLink with 14.4TB/s total interconnect bandwidth in its reference architecture material, giving the GPUs a high-bandwidth fabric inside the node before traffic ever leaves the chassis. (servethehome.com)

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The front of the 4U16X-GNR2 is busy in a very data-center-specific way. ServeTheHome noted 12 front 2.5-inch U.2 NVMe bays, with two connected to the CPU side and ten connected through the PCIe switch complex. ASRock Rack’s own product material for the 4U16X-GNR2/ZC B300 lists 10 hot-swap 2.5-inch PCIe 5.0 x4 NVMe bays through the PCIe switch, two hot-swap 2.5-inch PCIe 5.0 x4 NVMe bays through CPU1, and one M-key PCIe 5.0 x2 slot for 22110 or 2280 modules. The server also exposes management and low-speed platform networking in a flexible way, while the headline network feature is the row of eight OSFP 800Gb/s cages. That works out to 6.4Tb/s of front-panel network bandwidth before optional PCIe add-in cards are considered. (servethehome.com)

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This platform makes liquid cooling feel less like an exotic option and more like a practical requirement for compact Blackwell Ultra systems. The standard direct liquid cooling version uses cold plates on the CPUs and GPU tray, with leak-detection features around key hose and connection areas. ServeTheHome also showed that the GPU tray cooling is not only for the GPUs; the cold plates also cover components such as NVLink switches and ConnectX-8 SuperNICs. ASRock Rack has also shown a 4U16X-GNR2/ZC variant with ZutaCore HyperCool, a two-phase waterless direct liquid cooling approach using a non-conductive, non-corrosive dielectric fluid. That gives operators another direction if they want liquid cooling without water in the server loop. (servethehome.com)

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The power design underlines why these systems are infrastructure projects, not just servers. ServeTheHome reported ten 3kW 80 Plus Titanium power supplies, arranged for 5+5 redundancy, and observed more than 2kW at idle with workload power closer to 9kW in testing. ASRock Rack’s specification material also lists a 5+5, 3000W CRPS 80 Plus Titanium power-supply layout for the 4U16X-GNR2/ZC B300 platform. That does not make the system unusual for modern AI infrastructure, but it does make the planning visible: rack power density, facility cooling, coolant distribution, cabling, switch capacity, and service workflow all matter as much as the GPU count. For teams evaluating training or high-throughput inference nodes in 2026, the 4U16X-GNR2 is useful because it shows the whole package: dense compute, fast local networking, front NVMe, liquid-cooled thermals, and the operational weight that comes with Blackwell Ultra-class hardware. (servethehome.com)

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