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Verdict: FS’s PC015 is a passive, 1.5-meter QSFP112-to-QSFP112 copper cable for short, direct 400G links between compatible ports. ServeTheHome’s January 16, 2026 article is a useful physical inspection and deployment note—not a performance review: it reports no throughput, latency, error-rate, thermal, or interoperability measurements. The cable’s main appeal is a simple short-reach connection; its main practical drawback is the bulk and stiffness of 400G copper.
What ServeTheHome inspected
The reviewed product was the FS 400G QSFP112 passive DAC, model PC015, in a 1.5-meter length. ServeTheHome purchased two for direct, back-to-back connections between NVIDIA ConnectX-8 C8240 cards. The cable jacket was marked BizLink Special Cables Germany. These details describe the sample in that article; they do not establish that every length or cable in FS’s product range has been evaluated.
The article shows the cables and discusses their construction and use in the lab. The author notes that a 0.5-meter cable might have sufficed on the bench but chose 1.5 meters for more flexibility. The cables were described as not cheap, but the article does not provide a current price. Most importantly, it does not report measured link throughput, latency, BER, FEC behavior, sustained-load errors, temperature, bend-radius testing, or cross-vendor interoperability.
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QSFP112 is a connector and electrical-interface generation, not a claim that the complete cable carries only 112Gbps. A 400G QSFP112 connection uses four high-speed electrical lanes, each operating at roughly 100Gbps. In Ethernet contexts, related interface descriptions include 400GAUI-4 and 400GBASE-CR4. NVIDIA lists 400GAUI-4 C2M and 400GBASE-CR4 among supported ConnectX-8 C8240 Ethernet interfaces in its hardware specifications.
#1 Best Overall
- Compatible with NVIDIA DGX SPARK: Connect two compatible with DGX Spark systems through their QSFP network ports for high-speed inter-node communication. Suitable for desktop AI clustering, distributed inference, model
- UP TO 400GBPS CABLE CAPABILITY: QSFP112-to-QSFP112 direct attach cable compliant with the QSFP112 MSA and designed for 400G Ethernet applications. When used compatible with DGX Spark, the system establishes its supported 200GbE direct connection.
- 0.5M 30AWG PASSIVE COPPER CABLE: The short 1.64ft twinax cable is designed for equipment positioned side by side or within the same rack. Its passive construction requires no separate optical transceivers and consumes no more than 0.125W.
- ETHERNET AND INFINIBAND SUPPORT: Supports 400G Ethernet and compatible InfiniBand EDR/HDR applications. Actual speed and protocol depend on the connected network card, switch, firmware and port configuration.
- HOT-PLUGGABLE AND QUALITY TESTED: Supports hot insertion and removal for easier installation. Each cable undergoes quality inspection for signal integrity and connection performance. Confirm that your equipment uses compatible QSFP112 ports before ordering.
Do not treat QSFP112, QSFP-DD, and OSFP as interchangeable names:
- QSFP112: Uses four higher-speed lanes for a 400G link in this use case.
- QSFP-DD: Provides additional electrical contacts for double-density designs, commonly using eight lanes for 400G implementations.
- OSFP: A different form factor used, among other applications, for 800G ports. An OSFP-to-two-QSFP112 splitter is a distinct cable topology, not a straight QSFP112 DAC.
The “112” is associated with the approximate 112G-class signaling generation; it is not the aggregate bandwidth of this 400G cable. Connector resemblance alone does not prove that a cable fits, trains at the intended rate, or is supported by a particular platform.
Rank #2
- Compatible with NVIDIA DGX SPARK: Connect two compatible with DGX Spark systems through their QSFP network ports for high-speed inter-node communication. Suitable for desktop AI clustering, distributed inference, model development and fine-tuning workloads.
- UP TO 400GBPS CABLE CAPABILITY: QSFP112-to-QSFP112 direct attach cable compliant with the QSFP112 MSA and designed for 400G Ethernet applications. When used compatible with DGX Spark, the system establishes its supported 200GbE direct connection.
- 0.5M 30AWG PASSIVE COPPER CABLE: The short 1.64ft twinax cable is designed for equipment positioned side by side or within the same rack. Its passive construction requires no separate optical transceivers and consumes no more than 0.125W.
- HOT-PLUGGABLE AND QUALITY TESTED: Supports hot insertion and removal for easier installation. Each cable undergoes quality inspection for signal integrity and connection performance. Confirm that your equipment uses compatible QSFP112 ports before ordering.
- 【COMPATIBLE WITH DGX SPARK & GB10 AI SYSTEMS】Designed for QSFP/ConnectX-7 networking applications, Compatible with NVIDIA DGX Spark, compatible with ASUS Ascent GX10, compatible with Dell Pro Max with GB10, and compatible with Lenovo ThinkStation PGX.
The ConnectX-8 use case—and the breakout alternative
NVIDIA documents the ConnectX-8 C8240 as a dual-port QSFP112 SuperNIC supporting 400GbE and NDR-class InfiniBand operation, with supported modes depending on adapter model, configuration, firmware, and peer equipment. ServeTheHome contrasted it with the C8180, which uses a single OSFP 800Gbps port. The review’s straight PC015 cable addresses a one-port-to-one-port QSFP112 connection.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchThe same lab context included an NVIDIA SN5610 switch and an 800G OSFP-to-2×400G QSFP112 passive splitter cable. That splitter is appropriate when an 800G OSFP port must serve two independent 400G QSFP112 endpoints and the platform supports the required breakout mode. NVIDIA documents such splitter products and their four 100G-PAM4 channels per 400G side in its 800G cable documentation. It is not a substitute for a straight cable between two QSFP112 ports, and it requires compatible switch configuration, firmware, and endpoints.
Rank #3
- High-Speed AI Cluster Stacking Cable for NVIDIA DGX Spark / GB10 Systems - A high-speed, cost-effective Direct Attach Copper cable assembly for 400G short-reach interconnects. The passive design requires no retimers, delivering 400Gbps (4x 100G PAM4) connectivity with ultra-low power consumption for intra-rack and inter-rack links.
- Compatible with NVIDIA/Mellanox NJAAKK-N911 / NJAAKK-0006 / LMTQF022-SD-R and NVIDIA DGX Spark / GB10 Systems, including NVIDIA DGX Spark Founders Edition / Acer Veriton GN100 / ASUS Ascent GX10 / Dell Pro Max with GB10 / GIGABYTE AI TOP ATOM / HP ZGX Nano AI Station G1n / Lenovo ThinkStation PGX Workstation / MSI EdgeXpert. For detailed information, please refer to the Compatibility Table.
- As a passive DAC, it operates at <0.1W, generating negligible heat. This eliminates the need for active cooling on cables, reduces thermal load in crowded racks, and lowers overall power costs.
- Supports 400G Ethernet (IEEE 802.3ck) and InfiniBand NDR protocols. Ideal for connecting 400G switches to servers, routers, or storage in high-density data center environments, enabling high-bandwidth AI, HPC, and cloud infrastructure.
- Fully compliant with QSFP112 MSA standards and CMIS management interface. Each cable is individually tested for signal integrity and mechanical reliability to ensure plug-and-play compatibility with major 400G platforms.
| Topology | Use it when | Key check |
|---|---|---|
| QSFP112-to-QSFP112 passive DAC | Two nearby endpoints each have a compatible QSFP112 400G port and need one direct link. | Verify port, protocol, coding, supported reach, and platform qualification. |
| 800G OSFP-to-2×400G QSFP112 splitter | One 800G OSFP port must connect to two 400G QSFP112 endpoints. | Confirm the specific port supports 2×400G breakout and the cable is supported. |
Physical installation matters at 400G
ServeTheHome’s most practical observation is that this cable is physically substantial: it is much thicker and less flexible than familiar SFP+ or older QSFP DACs. That can complicate rack routing, cable-management-arm clearance, access to neighboring ports, connector strain, and airflow around dense port clusters. A length that looks generous on a bench may be awkward in a populated rack; a shorter cable is not automatically easier if it must make a tight turn immediately behind a port.
The article does not publish the manufacturer’s minimum bend radius or a measured jacket diameter. Check the current cable specification before routing, and do not force a bend or leave the connector carrying cable weight. Allow room to insert and remove adjacent cables and preserve the equipment maker’s airflow and temperature requirements. The C8240 documentation lists a 0°C–55°C operating range for the SuperNIC; that is not a temperature rating for the cable itself.
Rank #4
- A high-speed, cost-effective Direct Attach Copper cable assembly for 400G short-reach interconnects. The passive design requires no retimers, delivering 400Gbps (4x 100G PAM4) connectivity with ultra-low power consumption for intra-rack and inter-rack links.
- Supports 400G Ethernet (IEEE 802.3ck) and InfiniBand NDR protocols. Ideal for connecting 400G switches to servers, routers, or storage in high-density data center environments, enabling high-bandwidth AI, HPC, and cloud infrastructure.
- As a passive DAC, it operates at <0.1W, generating negligible heat. This eliminates the need for active cooling on cables, reduces thermal load in crowded racks, and lowers overall power costs.
- Fully compliant with QSFP112 MSA standards and CMIS management interface. Each cable is individually tested for signal integrity and mechanical reliability to ensure plug-and-play compatibility with major 400G platforms.
Compatibility checklist before buying
- Confirm the port form factor. Identify whether each end is QSFP112, QSFP-DD, or OSFP. Similar-looking high-speed ports are not enough.
- Confirm protocol and mode. Ethernet and InfiniBand support are not automatically interchangeable. Check that both endpoints support the intended protocol and 400G mode.
- Check the lane configuration. This cable is for a four-lane 400G QSFP112 link; do not assume it will work as a different lane arrangement or lower-speed mode without platform documentation.
- Verify reach and cable type. Passive copper has limited reach. The reviewed 1.5-meter sample does not establish the maximum supported distance for PC015 or any other length.
- Check cable coding and qualification. Some adapters and switches restrict or warn on unqualified cable EEPROM identities. NVIDIA’s validated-cables documentation is useful for supported NVIDIA configurations, but it does not prove FS PC015 is validated on every ConnectX-8 or third-party switch.
- Match firmware and breakout settings. Cable support and breakout behavior can depend on adapter and switch firmware. Check the documentation for the exact versions and topology deployed.
- Plan physical clearance. Account for connector access, airflow, cable routing, and strain relief before selecting length.
- Know what diagnostics are available. Make sure the platform can report module identification, negotiated lane state, and error counters so a marginal link can be investigated.
When to choose copper, a splitter, or optics
- Choose a straight passive QSFP112 DAC for a short one-to-one link when both ends have compatible QSFP112 ports, the cable’s rated reach covers the run, and the platform accepts its coding.
- Choose an OSFP-to-2×400G splitter only when one endpoint is an 800G OSFP port, two separate 400G links are wanted, and the host or switch supports that exact breakout configuration.
- Consider an active optical cable when a fixed point-to-point assembly is useful but passive copper reach or routing flexibility is inadequate, provided both endpoints support the AOC’s form factors and protocol.
- Consider optical transceivers and fiber for inter-rack or longer runs, flexible structured routing, or easier repatching. NVIDIA documents QSFP112 optical options, but the exact product and reach must match the deployment.
- Use QSFP-DD equipment and cabling where the platform requires it. A QSFP112 DAC is not a universal replacement for a QSFP-DD cable, even when both systems are described as 400G.
For vendor-supported deployments, compare the required topology and qualification list with the vendor’s own cable portfolio. NVIDIA’s LinkX cable information covers DACs, splitters, AOCs, and transceivers. For budget labs, a third-party cable may be attractive, but verify the exact model, coding, and support status rather than relying on connector appearance or a generic “400G” label.
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What a performance review would need to test
The ServeTheHome piece does not claim to establish performance or universal compatibility. A fuller evaluation would record whether both ends detect the cable and establish the intended protocol and rate; test cold boot, warm reboot, and reseat behavior; run sustained traffic; and monitor CRC, symbol, FEC, and retransmission counters. Throughput tests should document transport, packet size, stream count, CPU affinity, and whether the link is Ethernet or InfiniBand. A single ordinary throughput result would not by itself characterize every workload.
Best Value
- Compatible with NVIDIA DGX SPARK: Connect two compatible DGX Spark systems through their QSFP network ports for high-speed inter-node communication. Suitable for desktop AI clustering, distributed inference, model development and fine-tuning workloads.
- UP TO 400GBPS CABLE CAPABILITY: QSFP112-to-QSFP112 direct attach cable compliant with the QSFP112 MSA and designed for 400G Ethernet applications. When used with DGX Spark, the system establishes its supported 200GbE direct connection.
- 1M 30AWG PASSIVE COPPER CABLE: The short 1.64ft twinax cable is designed for equipment positioned side by side or within the same rack. Its passive construction requires no separate optical transceivers and consumes no more than 0.125W.
- ETHERNET AND INFINIBAND SUPPORT: Supports 400G Ethernet and compatible InfiniBand EDR/HDR applications. Actual speed and protocol depend on the connected network card, switch, firmware and port configuration.
- HOT-PLUGGABLE AND QUALITY TESTED: Supports hot insertion and removal for easier installation. Each cable undergoes quality inspection for signal integrity and connection performance. Confirm that your equipment uses compatible QSFP112 ports before ordering.
On Linux, ethtool <interface>, ethtool -i <interface>, and ethtool -S <interface> are useful starting points for interface information and statistics. NVIDIA-specific tools such as mlxlink or mstflint may offer additional diagnostics, but device paths and commands depend on the installed software stack, firmware, and operating mode. Any published test should state those versions and identify the exact cable sample and endpoints.
Bottom line
The FS PC015 is a plausible choice for a short, direct 400G link between compatible QSFP112 ports, especially in a lab or rack where passive copper is supported and its stiffness can be accommodated. ServeTheHome’s mini-review is valuable for seeing the product and understanding that physical constraint, but it supplies no benchmark or reliability evidence. Check the exact port type, protocol, firmware, cable qualification, reach, and routing requirements before ordering; choose a splitter or optical solution instead when the topology or distance calls for it.
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