QSA Adapters Get Even Better at 25Gb/s

100G, AOC, DAC, Ethernet, Link-X, Multi-mode, Single-mode, , , , , , , , , , , , , ,

QSA solves problems linking different port sizes and speeds equipment together

Problems: You have a 4-channel QSFP port on a switch or network adapter but you’ve got a single-channel subsystem that uses SFP and you want to connect older equipment, storage or a 10G device. Or you have a new shiny 25Gb/s-based Spectrum switch or ConnectX-4 or -5 network adapters and you want to connect to slower 10Gb/s equipment. How do you connect the different port types and speeds together?

Answer: Get the Mellanox QSA Adapter. QSFP-to-SFP Adapter – now supporting 25Gb/s!

Sometimes, the simplest things can solve big problems and frustrations. The QSA is one such device and costs less than a dinner for one.


What is a QSA?

The QSA is a Mellanox designed and patented, mechanical adapter that fits neatly inside a QSFP port and enables plugging in a smaller, single-channel SFP device into a QSFP 4-channel port.  Only the one-channel gets passed through even though the mechanical port is 4-channels.  The QSA contains a configuration EPROM to tell the host what it is and what speed to run at.  Unless one is configuring it to run a slower line rate, it is plug-and-plug again-and-play – nothing to configure in software.


Features and Notes

  1. QSAs are available in 2 versions: 10G and 25G.
    • 10G version also supports 1G
    • 25G version supports 1G and 10G
  2. QSA accepts a huge range of 10G and 25G cables and transceiver types:
    • CR DAC copper SFP (3-7m)
    • SR SFP multi-mode transceiver (100m)
    • SFP multi-mode AOCs (100m)
    • LR SFP single-mode transceiver (10km)
    • SX 1G SFP+ multi-mode transceiver (500m)
    • Base-T 1G SFP converter that uses CAT-5 copper UTP cables (100m)
  3. Passive and consumes no power
  4. Does not induce and signal latency delays
  5. Contains an EPROM to tell the switch port what it is – used in the initial configuration
  6. Only one channel passes through to the QSFP port
  7. Supports Ethernet-only as InfiniBand doesn’t generally use SFP single-channel links.
  8. There is even a DAC adapter cable with SFP on one end and QSFP on the other.
  9. MC2309130-xxx to 3m and to 3 meters and MC2309124-xxx to 7 meters.


The copper DACs have a maximum reach of 3 – 7 meters but with a LR transceiver module with single-mode fiber can reach as far a 10km or 6.25 miles!

10G and 25Gb/s Cables and Transceivers Options For Use in QSA Adapters


In the past, Mellanox offered network adapters in SFP and QSFP versions of the cards. But starting with ConnectX-6, only the QSFP28 versions will be offered and if a SFP single-channel is required, the QSA will be the solution to create the connection.


Not everything in the world runs or needs to run at 25Gb/s so the QSA is a neat way to link slower 10G sub-systems to new high-speed Spectrum switches and ConnectX-5 network adapter and later upgrade the slower equipment to 25Gb/s.

More Information: 

LinkX is the Mellanox trademark and name for its cables and transceivers product line



About Brad Smith

Brad is the Director of Marketing at Mellanox, based in Silicon Valley for the LinkX cables and transceivers business focusing on hyperscale, Web 2.0, enterprise, storage and telco markets. Recently, Brad was Product Line Manager for Intel’s Silicon Photonics group for CWDM4/CLR4 and QSFP28 product lines and ran the 100G CLR4 Alliance. Director of Marketing & BusDev at OpSIS MPW Silicon Photonics foundry. President/COO of LuxSonar Semiconductors ( Cirrus Logic) and co-founder & Director of Product Marketing of NexGen, a X86-compatible CPU company sold to AMD - now the X86 product line. Brad also has ~15 years in technology market research as Vice president of the Computer Systems group at Dataquest/Gartner; VP/Chief Analyst at RHK and Light Counting networking research firms. Brad started his career at Digital Equipment near Boston with the VAX 11/780 and has served as CEO, president/COO and on the board-of-directors of three start-up companies. Brad has a BSEE degree from the University of Massachusetts; MBA from University of Phoenix and holds 2 optical patents

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