The inference cluster, in detail.
How four 128 GB AMD Ryzen AI Max+ 395 nodes are engineered into one coordinated distributed-inference system. Every figure states its operating conditions — deliberately. Numbers without conditions are marketing; numbers with conditions are engineering.
One node, specified from the vendor sheet.
Per-node figures follow AMD's published processor specifications. System-level I/O — in particular USB4 v2 / 80 Gbps ports — is a vendor-board property, so we verify it per chassis rather than inheriting it from the CPU page.
Local memory is 25–40× faster than any external fabric.
This single ratio drives the whole architecture. The runtime keeps tensors home and crosses only when it must — which is also why adding fabric bandwidth never buys linear tokens/s, and why we engineer topology to the model's traffic pattern instead of quoting a headline link speed.
Linear scale, theoretical figures — the gap is the point. Distributed inference works here because llama.cpp RPC shards layers so the heaviest traffic stays inside each node.
Three fabrics, engineered — not just cabled.
USB4 v2 for cost, Dual 25GbE for repeatable four-node operation, hybrid multi-path for maximum headroom on selected pairs. Each carries its topology, its strengths and its honest constraints.
USB4 v2 direct-link
USB4 host-to-host networking (USB4NET) lets two systems joined by a certified cable talk like Ethernet peers — no NIC, no switch. Ideal for a two-node pilot; the cheapest path to private local AI.
PCIe Dual 25GbE fabric
An ENPBA-class PCIe card per node — Intel E810-class controller, two 25GbE SFP28 ports and two M.2 NVMe slots — through a compact SFP28 switch. Standard Ethernet means standard tooling: bonding, MTU tuning, per-port monitoring. The recommended default for a production ArrayMeld 4.
Hybrid multi-path
The full 25GbE switch backbone still reaches every node — so the controller talks to all workers — and the controller adds direct USB4 links to accelerate its heaviest worker paths. Each board exposes two USB4 ports, so the controller can direct-link at most two workers; any remaining node rides the fabric. Reserved for the traffic patterns that justify the extra engineering, and only there.
The stack AMD's own cluster guide runs — tuned by us.
Linux is the serious path for multi-node work: full control of interfaces, MPTCP, routing and kernel parameters, and the best ROCm alignment for this platform. Each release records its exact versions and is regression-tested before it becomes supported.
# build llama.cpp with HIP + RPC (per node) cmake -B rocm -DGGML_HIP=ON -DGGML_RPC=ON \ -DAMDGPU_TARGETS="gfx1151" cmake --build rocm --config Release -j$(nproc) # workers — isolated private segment only ./rpc-server -p 50053 -c --host 0.0.0.0 # controller — GLM-5.2 across three workers ./llama-server -m GLM-5.2-Q4.gguf -c 32768 \ -fa on -ngl 999 --port 8080 \ --rpc 10.25.0.2:50053,10.25.0.3:50053,10.25.0.4:50053
Why two nodes is the floor and four is the recommendation.
Model fit is arithmetic before it is anything else: weights plus KV cache plus runtime overhead must live inside aggregate node memory, with headroom. The ladder below is sized from public GGUF figures, then verified on the real system.
| Deployment target | Nodes / aggregate | On-disk weights | Positioning |
|---|---|---|---|
| GLM-5.2 Q2 / 2-bit GGUF | 2 × 128 GB — 256 GB | ≈ 238–254 GB | Entry / validation — deliberately tight; context budget controlled and measured |
| GLM-5.2 4-bit / W4-class | 4 × 128 GB — 512 GB | ≈ 365 GB+ | Recommended production coding-agent target — headroom for KV cache, context and runtime |
| 8-node dual-fabric | 8 × 128 GB — 1,024 GB | ≈ 700–900 GB class | Scale-out custom engineering — capacity, precision and context scale; per-token latency does not |
| Larger / future open models | 4+ nodes or custom | Model-specific | Custom engineering with model-specific validation before commitment |
Every cluster leaves with numbers attached.
We do not publish tokens/s until it is measured on the final hardware, model, quantisation, context length, runtime version and topology — and neither should anyone else. Here is what gets measured.
Two-node validation (entry tier)
- USB4NET single-path and dual-link iperf3, then MPTCP-aggregated
- 25GbE per-port and multi-flow iperf3
- llama.cpp RPC over single path, then over MPTCP
- GLM-5.2 Q2 load, time-to-first-token, tokens/s, stability
- Memory, temperature and power monitored throughout
Four-node validation (recommended tier)
- All-node 25GbE validation; jumbo frames / LACP / MPTCP where used
- llama.cpp RPC with 2, 3 and 4 workers
- GLM-5.2 4-bit-class model loading and long-context stability
- Coding-agent workflow test — Hermes or OpenClaw
- Recovery after worker restart; NVMe staging performance
Our claim matrix, published on purpose.
An audience that reads spec sheets deserves a vendor that writes them honestly. These are the wording rules we hold ourselves to — on this site, in quotes, and in person.
| Topic | We say | We won't say |
|---|---|---|
| Memory | 512 GB aggregate memory-class capacity across four 128 GB nodes | "512 GB unified VRAM" |
| Model scale | Designed for large low-bit open models, subject to validation | "Guaranteed to run every 400B model" |
| GLM-5.2 | Current recommended target as of July 2026 | "Permanently the best model" |
| USB4 v2 | Up to 80 Gbps raw direct-link capability where the platform supports it | "Guaranteed 80 Gbps application throughput" |
| Dual 25GbE | Up to 50 Gbps aggregate capacity per node | "Every stream runs at 50 Gbps" |
| Hybrid fabric | 100 Gbps+ class multi-path on selected pairs, subject to validation | "Automatic 130 Gbps connection" |
| Vs closed models | Strong enough for many practical local coding-agent workflows | "Equal or superior to closed frontier models" — unless our benchmarks show it on your workload |
Where the figures come from.
Hardware, pricing, model rankings and software support all move. We re-check these before publishing final claims — and we recommend you click through and do the same.
16 Zen 5 cores, 128 GB max, 256-bit LPDDR5x-8000, Radeon 8060S (40 CUs), PCIe 4.0, native USB4 listing.
amd.com — product pageFour 128 GB Ryzen AI Max+ 395 systems, Ubuntu 24.04, ROCm and llama.cpp RPC running a trillion-parameter-class quantised model over Ethernet.
amd.com — technical articleSupported gfx1151 / Ubuntu / ROCm combinations and validated data types.
rocm.docs.amd.comUSB4 interdomain networking: two USB4 PCs joined by a cable enumerate a network adapter and communicate like Ethernet peers.
learn.microsoft.comMPTCP can use multiple interfaces within a single connection, aggregating bandwidth or preferring lower-latency paths.
docs.kernel.orgrpc-server exposes remote devices for distributed inference; upstream flags the backend proof-of-concept and insecure on open networks.
github.com — llama.cppA source link does not freeze a specification. Before we rely on any figure for a contract or claim, we open the current official source, record the date, and validate it on the delivered system.
Bring your target model. We'll design the cluster around it.
Send your target model, context requirements and budget path — we'll return a scoped topology, a bill of materials, and the validation plan we would sign off against.