OSFP vs. QSFP-DD: A Practical Breakdown for GPU Clusters

You know that drawer in every house with a pile of chargers in it? Somehow one of them is for a phone, and one of them is for a vacuum, and they look almost identical — same size, same general shape — but plug the wrong one into the wrong device and nothing happens. OSFP and QSFP-DD are the data center's version of that drawer. Same rack, same general job, and yet swapping them gets you a cable that just sits there, not seated, not working, quietly judging your procurement process.

Short version: OSFP and QSFP-DD are both capable of 400G/800G speeds, but they are physically different connectors and are not interchangeable without an adapter. NVIDIA's higher-end GPU and switch silicon increasingly ships in OSFP, while a large share of existing data center switch ports remain QSFP-DD. Before ordering interconnect cable, confirm the port type on both ends of the link — not just the GPU or NIC side.

Why This Trips People Up

Many buyers assume "400G cable" is a single spec. It isn't. The connector shape, power envelope, and thermal design differ enough between OSFP and QSFP-DD that ordering the wrong one means a cable that physically won't seat in the port.

OSFP — Octal Small Form Factor Pluggable

• Larger connector with a higher power envelope and more thermal headroom for high-speed optics
• Increasingly common on newer NVIDIA GPU and switch platforms
• Trade-off: larger, heavier modules can be tighter to route and pull in dense racks

QSFP-DD — Quad Small Form Factor Pluggable Double Density

• Widely deployed across existing switch infrastructure
• Backward-compatible path with QSFP28/56 in many switches
• Lower power ceiling than OSFP at the highest speeds

And Then There Is QSFP112

A third form factor sits alongside these two on NVIDIA's NDR-generation gear, and it is the one that produces the most expensive ordering mistakes: QSFP112. It carries the same 4×100G PAM4 signalling as a 400G OSFP module in a QSFP-sized shell.

The part worth memorising: a BlueField-3 DPU is QSFP112 only. NVIDIA states plainly that BlueField-3 adapters accept QSFP112 devices and that OSFP is not for use in BlueField-3 DPUs. A ConnectX-7 also ships in both OSFP and QSFP112 variants. So "400G NVIDIA adapter" does not tell you the form factor — the 400G SR4 module for a QSFP112 host is the MMA1Z00-NS400, not the OSFP MMA4Z00-NS400. Same optics, same MPO-12/APC fiber, a cage that will not accept the other part. We stock it at $549.

One more thing QSFP112 does not have: a flat-top/finned-top question. That distinction belongs to the OSFP family, where the issue is whether the module or the port cage carries the heatsink. QSFP112 has one shape.

How to Check What You Actually Need

Before ordering, work through this checklist: confirm your switch's port spec sheet, confirm your NIC or GPU's port spec sheet, match the cable's form factor to both ends, and when in doubt, ask before ordering rather than after a mismatched cable arrives.

FAQ

Can I use an OSFP-to-QSFP-DD adapter?

Limited adapter options exist, but they aren't universal across every speed and vendor combination. Confirm compatibility with a specialist before relying on one.

Which does NVIDIA use?

It varies by platform and generation. DGX systems and newer high-density platforms trend toward OSFP, but plenty of deployed hardware still uses QSFP-DD — and NVIDIA's NDR adapters add QSFP112 as a third option.

Does a BlueField-3 use OSFP or QSFP112?

QSFP112, always. NVIDIA states that BlueField-3 adapters accept QSFP112 devices only and that OSFP is not for use in BlueField-3 DPUs. The 400G SR4 module for one is the MMA1Z00-NS400 at $549, not the OSFP MMA4Z00-NS400.

Will my existing DAC cables work if I upgrade my switch?

That depends entirely on the new switch's port type, not just its speed rating. A speed match doesn't guarantee a connector match.

How much do OSFP and QSFP-DD parts cost?

At Resilient Tec, the OSFP MMA4Z00-NS400 is $579, the QSFP112 MMA1Z00-NS400 is $549, the OSFP MMA4Z00-NS is $829 and the QSFP-DD MCP1660-W001E30 DAC is $119. All are new compatible parts. (Prices checked October 12, 2026.)

Where can I buy OSFP, QSFP112 or QSFP-DD optics and cables?

Directly from Resilient Tec: MMA4Z00-NS400 — $579 · MMA1Z00-NS400 — $549 · MMA4Z00-NS — $829 · MCP1660-W001E30 — $119

Related Hardware / You Might Also Need

Confirming your port type is step one — here's where to shop once you know what you need:

• Browse All Interconnects — current DAC, AOC, and transceiver inventory, including QSFP-DD options
• Shop DAC Cables
• Shop AOC Cables
• MPO-12/APC vs UPC fiber for NDR optics — once you have the right module, this is the cable that goes between them
• NVIDIA OSFP part-number crosswalk — every part number in this range mapped to form factor and which end of the link it belongs in

OSFP optics are now in stock: the 400G OSFP SR4 flat-top (RHS) for the ConnectX-7 NIC side, and the 800G OSFP SR8 finned-top (IHS) for the Quantum-2 switch side — plus the 400G QSFP112 for BlueField-3. If you're not sure which of the OSFP pair a given port takes, this guide sorts it out in about a minute.

Ready to Buy?

Prices below checked October 12, 2026 — sold directly by Resilient Tec at resilient-tec.com.

• MMA4Z00-NS400 — 400G OSFP SR4 flat-top (RHS), compatible — $579, ConnectX-7 end
• MMA1Z00-NS400 — 400G QSFP112 SR4, compatible — $549, BlueField-3 and ConnectX-7 QSFP112 end
• MMA4Z00-NS — 800G OSFP SR8 finned-top (IHS), compatible — $829, Quantum-2 end
• MCP1660-W001E30 — 400G QSFP-DD passive DAC, 1 m — $119, QSFP-DD in-rack
• MPO-12/APC OM4 multimode trunk cable — Type B, female-to-female — $59.00 (1 m) to $139.00 (20 m), the fiber for the optics above

Not sure if your gear needs OSFP, QSFP-DD or QSFP112? Send us your switch and GPU/NIC model and we'll confirm before you order.

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