Short answer: OSFP is the connector. DAC and AOC are two of the four things that can live between two connectors. An OSFP DAC, an OSFP AOC and an OSFP transceiver are all OSFP — so "OSFP or DAC?" has no answer as asked. The question you actually need to answer is: which cage does my port have, how far is the run, and how many watts and RMAs am I willing to pay?
Jump to what you need:
- 1. Which cage do I have? — OSFP, QSFP-DD, QSFP112
- 2. Which medium? — DAC, ACC, AEC, AOC, transceiver + fiber
- 3. The distance ladder — what to buy at 1 m, 3 m, 10 m, 100 m
- 4. The twin-port trap — why one OSFP cable is sometimes two links
- 5. The cost nobody prices — field serviceability
- 6. Buy by distance — parts, prices, stock
Why the comparison doesn't work
Three independent decisions get collapsed into one question, and the collapse is where money gets lost:
| Axis | What it is | Examples |
|---|---|---|
| Form factor | The plug and the cage it goes into. Mechanical and thermal. Says nothing about speed or medium. | SFP28, QSFP28, QSFP56, QSFP112, QSFP-DD, OSFP, OSFP-XD |
| Medium | What carries the signal between the two ends. | Passive DAC, ACC, AEC, AOC, transceiver + fiber |
| Line rate & lane structure | How many electrical lanes at what rate. | 4 × 100G PAM4 = 400G · 8 × 100G = 800G · 8 × 200G = 1.6T |
The same OSFP shell carries 400G, 800G and 1.6T. It carries passive copper and it carries single-mode optics out to 500 m. So "OSFP is better for long distances" is not a true statement or a false one — it's a category error, the same shape as asking whether you want a wall outlet or electricity.
This is not a pedantic point. It is the error behind the most expensive interconnect mistake we see: a team buys the right module in the wrong cage. An NVIDIA BlueField-3 DPU accepts QSFP112, not OSFP — NVIDIA's own documentation is explicit that "OSFP is not for use in BlueField-3 DPUs." A 400G OSFP SR4 and a 400G QSFP112 SR4 are optically identical parts. One fits your DPU. One does not. (We have the full breakdown in Does the MMA4Z00-NS400 Work With My System?)
1. Which cage do you actually have?
Start here, because this is the decision with no workaround. There is no adapter. Check the host, not the switch — the two ends are often different.
| Cage | Typically found on | Lanes | Notes |
|---|---|---|---|
| OSFP | ConnectX-7, ConnectX-8, Quantum-2 QM9700/QM9790, DGX H100/H200, Quantum-X800 | 8 | Bigger shell, better thermals, supports twin-port. Comes in flat-top (RHS) and finned-top (IHS) — not interchangeable. |
| QSFP112 | BlueField-3 DPUs, ConnectX-7 QSFP112 adapters | 4 | 400G in a QSFP-sized cage. The part people buy in OSFP by mistake. |
| QSFP-DD | Ethernet switching — Cisco, Arista, Juniper, Spectrum | 8 | Backward compatible with QSFP28/56. Full comparison here. |
| QSFP56 / QSFP28 | HDR 200G and 100G fabrics, DGX Spark | 4 | Where most existing fleets still live. |
Browse by cage: Transceivers · DAC Cables · AOC Cables · Breakout Cables · All Interconnects
2. Then pick the medium — there are four, not two
Most comparison articles give you two options: DAC or AOC. The real menu has four, and the two in the middle are where the money is, because they cover exactly the 3–7 m range where passive copper has already died and optics are still overkill.
| Medium | What it is | Practical reach | Power | Relative cost |
|---|---|---|---|---|
| Passive DAC | Twinax copper, no electronics. EEPROM at each end. | ~1–3 m depending on rate | ~0 W | $ |
| ACC / LACC | Active copper. A re-driver or linear amplifier in the plug. | ~3–5 m | ~1–2 W per end | $$ |
| AEC | Active electrical. A full retimer DSP in the plug. | ~5–7 m | ~3–5 W per end | $$$ |
| AOC | Optics permanently bonded to fiber. One sealed assembly. | Tens of metres to ~100 m | ~8–15 W per cable | $$$$ |
| Transceiver + fiber | Two pluggable modules, separate structured fiber. | 100 m MMF · 500 m DR4 SMF | ~8.5 W per 400G module · ~15 W per twin-port | $$$$$ |
Naming caution: vendors are not consistent. NVIDIA's LinkX catalog uses ACC and LACC; much of the market says AEC for anything retimed. If a datasheet says "active copper," find out whether there is a re-driver or a retimer in it before you trust the reach number. We go deeper in DAC vs AOC vs AEC: Which Cable Goes Where in an AI Rack?
3. The distance ladder
These are planning numbers for passive copper, not guarantees — insertion loss depends on gauge, bend radius and how forgiving the host's SerDes is. Measure the actual cable path, including slack and the trip through the cable manager, not the straight line between racks.
| Link rate | Passive DAC works to roughly | Past that, go to |
|---|---|---|
| 200G (4 × 50G) | ~3 m | ACC, then AOC |
| 400G NDR (4 × 100G PAM4) | ~1–2 m, sometimes 3 m | ACC / AEC, then SR4 optics |
| 800G (8 × 100G PAM4) | ~1–2 m | ACC / AEC, then SR8 or 2×DR4 optics |
| 1.6T (8 × 200G) | ~1 m or less | Optics, effectively |
The practical consequence: at 800G, copper is an intra-rack medium. If your design has a 4 m copper run in it, the design is wrong, not the cable. That one table is why "copper where you can, optics where you must" is a real constraint and not a slogan.
4. The twin-port trap
This is the part that breaks every per-link cost comparison published on the subject, and almost nobody mentions it.
An NVIDIA twin-port OSFP module or cable looks like one thing and behaves like two. A single twin-port 800G OSFP carries two independent 400G links. That is how a 32-cage Quantum-2 QM9700 presents 64 NDR ports. So when you compare "one 800G DAC at $298 versus two 400G optics at $579 each," you are not comparing like for like unless you have counted ports rather than cables.
What this means in practice:
- A twin-port OSFP breakout DAC is often the cheapest 400G-per-port in the building — if both ends land within 2 m.
- The switch-side module is finned-top (IHS); the NIC-side module is flat-top (RHS). Ordering the wrong one is the second most common mistake after cage confusion.
- A twin-port optic needs two MPO-12/APC cables, not one. Budget the fiber.
Twin-port parts in stock now:
- MCP7Y00-N002 — 800G twin-port OSFP to 2×400G OSFP passive breakout DAC, 2 m — $298.45
- MCP7Y50-N001 — 800G OSFP to 4×200G OSFP passive breakout DAC, 1 m — $384.00
- MMA4Z00-NS — 800G OSFP SR8 twin-port finned-top (IHS), for QM9700/QM9790 — $829.00
5. The cost nobody prices: field serviceability
A DAC and an AOC are sealed assemblies. The optics in an AOC are bonded to the fiber at the factory. When one end fails, you do not swap a module — you pull the entire cable out of the cable management, out of the rack, and run a new one. At 3 a.m., through a populated rack, with the fabric degraded.
Transceivers plus structured fiber cost more up front and are repairable one module at a time. The fiber stays in the tray. You swap a $579 part in ninety seconds without touching anything else.
At eight links this does not matter. At eight hundred it dominates, and it never appears in the cost-per-link table that every vendor publishes. If your cluster has a growth plan, price the mean time to repair alongside the cable.
Power and heat are a budget line too
Optics are a thermal load you pay for twice — once at the PSU, once at the CRAC. A 400G OSFP SR4 draws around 8.5 W; a twin-port 800G module around 15 W. Populate all 32 cages of a QM9700 with twin-port optics and you have added roughly 480 W of optics to that one rack unit. Copper adds zero. This is the real reason NVIDIA keeps copper in the rack rather than a cost-cutting preference — see what GTC 2026 said about copper.
And the EEPROM applies to cables too
People assume coding is a transceiver problem. It isn't — DACs and AOCs carry EEPROM at each end, and a Quantum-2 will reject a cable whose EEPROM it doesn't recognize exactly as fast as it rejects a module. "Any OSFP DAC" is not a purchasing specification. See what to check before buying compatible NDR parts and why the same part works in one switch and not another.
6. Buy by distance
Prices and stock verified 2026-09-21. Free U.S. shipping; every part is tested and programmed before it ships.
Under 2 m — passive OSFP DAC
| Part | What it is | Price |
|---|---|---|
| MCP4Y10-N001 | OSFP 400G NDR passive DAC, 1 m — DGX H100/H200 | $195.00 |
| MCP4Y10-N002 | OSFP 400G NDR passive DAC, 2 m | $243.99 |
| MCP7Y00-N002 | 800G twin-port OSFP to 2×400G OSFP breakout DAC, 2 m | $298.45 |
| MCP7Y50-N001 | 800G OSFP to 4×200G OSFP breakout DAC, 1 m | $384.00 |
Other cages: 400G QSFP-DD passive DAC, 1 m — $119.00 · 200G QSFP56 passive DAC, 1 m — $87.45 · all 49 DAC cables
3–7 m — active copper
ACC and AEC at 400G and 800G are built to order against the specific host and switch pair. Tell us the two endpoints and the length and we will quote the correct coding rather than sell you a passive cable that will not train. Request a quote →
Beyond copper — optics and fiber
| Part | What it is | Price | Stock |
|---|---|---|---|
| MMA4Z00-NS400 | 400G OSFP SR4 flat-top (RHS), MMF — ConnectX-7 NIC side | $579.00 | In stock |
| MMA4Z00-NS | 800G OSFP SR8 twin-port finned-top (IHS) — Quantum-2 switch side | $829.00 | In stock |
| MMA1Z00-NS400 | 400G QSFP112 SR4, MMF — the BlueField-3 part | $549.00 | Sourcing — quote |
| MMS4X00-NS400 | 400G OSFP DR4 flat-top, single-mode, 500 m | $809.00 | Sourcing — quote |
| MMS4X00-NM | 800G OSFP 2×DR4 twin-port, single-mode, 500 m | $999.00 | Sourcing — quote |
Optics need the right fiber, and it is probably not the fiber you own. NDR optics use angle-polished (APC) MPO-12. UPC cords from a 100G or 200G fabric will not mate with them — this is the single most common reason a correctly ordered optic won't link on install day.
- MPO-12/APC OM4 multimode trunk, Type B — 1 m to 20 m, from $59.00, in stock
- MPO-12/APC OS2 single-mode trunk, Type B — for DR-class optics, from $55.00
- MPO-12/APC 1:2 splitter cables — MFP7E20 equivalent, built to order
- Why the polish matters: MPO-12/APC vs UPC
AOC — when the run is long and you want one part number
- MFA7U10-H003 — 400G OSFP to 2×200G QSFP56 active optical breakout, 3 m — $1,345.45. The NDR-to-HDR bridge part; why it exists.
- All AOC cables — 100G, 200G and 25G assemblies in stock
- Custom coding on both ends: double-programmed DAC and AOC
The decision in four questions
- What cage is on each end? Check the host, not the switch. OSFP and QSFP112 are not interchangeable and there is no adapter.
- How long is the actual cable path? Under 2 m at 400G/800G, use passive copper. 3–7 m, active copper. Beyond that, optics.
- How many links, and who fixes them at 3 a.m.? Past a few dozen links, transceivers plus structured fiber beat sealed assemblies on total cost even though they lose on unit price.
- Flat-top or finned-top, and how many ports per cage? Switch side is finned (IHS), NIC side is flat (RHS), and a twin-port module is two links needing two fiber runs.
Not sure on any of the four? Send us the switch model, the NIC or DPU model, and the rack distance. We will tell you the part number — and if the honest answer is a cheaper medium than the one you asked about, we will tell you that too. Get a quote →
FAQ
Is OSFP better than DAC?
The question doesn't resolve. OSFP is a connector form factor; DAC is a cable medium. An OSFP DAC is both at once. What you are probably asking is whether copper or optics suits your run — under about 2 m at 400G or 800G, copper; beyond that, optics.
Can I use an OSFP DAC in a QSFP-DD port?
No. They are different cages with different mechanics and thermals, and no adapter exists. QSFP-DD is backward compatible with QSFP28 and QSFP56; it is not compatible with OSFP.
Will an OSFP transceiver work in a BlueField-3 DPU?
No. NVIDIA's documentation states that OSFP is not for use in BlueField-3 DPUs — they take QSFP112. The equivalent part is the MMA1Z00-NS400, optically identical to the OSFP SR4 in a different cage.
What is the difference between ACC and AEC?
Both are active copper. ACC generally uses a re-driver or linear amplifier and reaches roughly 3–5 m; AEC uses a full retimer DSP and reaches roughly 5–7 m at higher power and cost. NVIDIA's LinkX catalog uses ACC and LACC; much of the rest of the market says AEC for anything retimed, so check the datasheet rather than the acronym.
How far can an 800G passive DAC actually run?
Plan on 1–2 m. Copper at 800G is an intra-rack medium. If the design calls for 4 m of copper, the design needs changing, not the cable.
Is a DAC or AOC cheaper than transceivers and fiber?
Per link, at install, almost always yes. Over the life of a large fabric, often no: a DAC or AOC is a sealed assembly, so a single failed end means pulling and re-running the whole cable, while a transceiver is a ninety-second swap with the fiber left in place.
Do DAC and AOC cables need to be coded for my switch?
Yes. Both carry EEPROM at each end, and switches reject unrecognized cables the same way they reject unrecognized optics. We program and test every assembly for the specific platform pair before it ships.
Related reading
- OSFP DAC Cables: What They Are, When to Use One, and When They'll Quietly Ruin Your Week
- OSFP vs QSFP-DD: A Practical Breakdown for GPU Clusters
- DAC vs AOC vs AEC: Which Cable Goes Where in an AI Rack?
- Flat-Top or Finned-Top OSFP? How to Tell Which Module Your ConnectX-7 Needs
- Layer 1 Decoded: Every Physical Form Factor in a Modern Rack
- MPO-12/APC vs UPC: Why Your Existing Fiber Won't Work With NDR Optics
- 800G AI Fabric Buying Guide: Copper Where You Can, Optics Where You Must
- What Cable Do I Need? The Complete Guide to GPU Cluster Interconnects
- NVIDIA OSFP Part-Number Crosswalk: Mellanox MMA/MMS to NVIDIA 980- Numbers
- NVIDIA & Mellanox Interconnect Compatibility Guide
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