{"id":"cable-cartridge","level":"rack","name":"NVLink copper cable cartridge","shortName":"Cable cartridge","role":"Provides dense physical signal connections between compute and switch trays.","description":"A rack-wide fabric needs a physical transmission path as well as switch chips. The GB200 system uses a passive copper cable-cartridge backplane with blind-mate tray connections. That arrangement concentrates many short high-speed paths in a managed assembly rather than requiring every tray connection to be manually routed as an exposed cable. The atlas reveals the cartridge as a dense set of point-to-point paths and distinguishes it from the logical network drawn on top. Copper is not inherently obsolete: appropriate short-distance links can be effective, while optical links serve other reaches and system requirements. Connector integrity, signal quality, topology, and service access all affect whether theoretical bandwidth becomes reliable communication.","specs":[{"label":"GB200 link medium","value":"Passive copper","context":"Rack-scale NVLink cable-cartridge backplane."},{"label":"Tray connection","value":"Blind-mate connectors","context":"Documented rear-side connection scheme."},{"label":"Published scale","value":"Over 5,000 copper cables","context":"NVIDIA rack description; illustration samples paths for legibility."}],"interfaces":[{"name":"Compute-tray connectors","direction":"in","signal":"High-speed electrical signals"},{"name":"Switch-tray connectors","direction":"out","signal":"Mapped physical NVLink paths"}],"tradeoff":"Short copper paths can serve dense racks well. Signal integrity and connector complexity constrain physical design.","whyAI":"Dense model communication requires real conductors and connectors. Cabling makes the rack fabric physically realizable.","related":["rack","compute-tray","nvlink-switch","optics"],"sources":[{"title":"NVIDIA — Blackwell Rack-Scale Interconnection","url":"https://blogs.nvidia.com/blog/blackwell-ai-inference/"},{"title":"NVIDIA — DGX GB Rack Scale Systems Hardware Guide","url":"https://docs.nvidia.com/dgx/dgxgb200-user-guide/hardware.html"},{"title":"NVIDIA — DGX GB200 SuperPOD Components","url":"https://docs.nvidia.com/dgx-superpod/reference-architecture-scalable-infrastructure-gb200/latest/dgx-superpod-components.html"}],"scale":"Meter-scale cable assembly containing many short links","kind":"cable-cartridge","mechanism":["Map GPU endpoint connections to the required switch connections.","Bundle the physical copper paths into the cartridge structure.","Mate trays to the backplane so the logical fabric has a continuous signal path."],"misconception":"A drawn connection is not merely abstract: a working rack needs its physical conductor, connectors, and signal margins.","check":{"question":"Why does the atlas sample the cable paths?","options":["Thousands of physical paths would obscure the topology at viewing scale","The rack has only one real cable","Each visible cable represents a neural-network layer"],"answer":0,"explanation":"The reference rack contains thousands of cables. A sampled rendering preserves the structural lesson without pretending to show every conductor."},"branch":"Rack integration","subbranch":"Physical signal paths","science":[{"title":"Propagation and serialization","equation":"t_link ≳ L / v_prop + S / B_payload","explanation":"A link has propagation time along its length and serialization time to place the payload onto the channel. Short distance does not remove serialization or protocol overhead.","assumptions":"Simple one-hop link model; buffering, coding, connector loss, retransmission, and routing can add further cost."}],"history":[],"prerequisites":["nvlink-port","interconnect"],"learningObjective":"Separate propagation delay from serialization time on a physical link.","engineeringExample":"Synthetic one-hop link: 2 m at an assumed propagation speed of 2 × 10⁸ m/s adds 10 ns. Serializing a 1 kB payload at 25 GB/s adds 40 ns. Their sum is 50 ns before coding, connectors, buffering or retransmission.","evidenceNotes":"Length, speed and payload rate are teaching assumptions rather than specifications for a cable cartridge. A physical cable route is distinct from the logical collective or network topology that uses it.","labId":"library","scope":"Use the execution investigation for the shared tensor-to-memory-to-result thread; no current standalone calculator models this lesson’s full mechanism.","investigationId":"execution","labScope":"Use the execution investigation for the shared tensor-to-memory-to-result thread; no current standalone calculator models this lesson’s full mechanism."}