NVIDIA SLI GeForce RTX 2080 Ti and RTX 2080 with NVLink Review 61

NVIDIA SLI GeForce RTX 2080 Ti and RTX 2080 with NVLink Review

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The NVLink SLI Bridge


NVIDIA's NVLink bridge shares some of its design language with the latest GeForce RTX "Founders Edition" graphics cards. It comes in two physical sizes, depending on how much spacing there is between your two graphics cards and the PCIe slots they're installed in.


With "Volta" and "Turing," NVIDIA is implementing the 2nd generation NVLink protocol with up to two 8-lane sublinks. The TU102 supports two x8 sublinks making up one link (making it mesh-capable in its Quadro RTX avatar) and is theoretically capable of 300 GB/s, while the TU104 supports just one x8 link capable of up to 150 GB/s. On the GeForce RTX 20-series GPUs, NVIDIA is either using fewer lanes or lower clocks since it doesn't envision setups with more than 2 GPUs. The RTX 2080 Ti SLI hence has 100 GB/s bi-directional NVLink bandwidth, while the RTX 2080 SLI has 50 GB/s.

Disassembly


The NVLink bridge has a C-shaped design, unlike SLI-HB bridges that were rectangular. The NVLink connector has a higher pin-count (124 pins) compared to SLI-HB (52 pins), yet the fiberglass PCB looks narrower because it's probably multi-layer and uses vias near the connectors. This explains why you don't see flexible NVLink bridges printed on polyethylene substrates as those would need to be single-layer, running the entire width of the NVLink connector and resembling an ugly ribbon cable, such as IDE, hampering airflow for the Founders Edition axial-flow cooler.


There seem to be two tiny chips responsible for the LED lighting inside the shroud. This is purely cosmetic as it could at best indicate that an SLI link is active between two GPUs. The NVLink bridge is still a "dumb" piece of hardware, like a cable, and has no real logic of its own. Asking $79 for this is quite outrageous.
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