HP 670759-B21 — 0.5m InfiniBand FDR QSFP+ Passive Copper Cable (DAC)
Technical Identity
The HP 670759-B21 is an HP-branded 0.5-meter InfiniBand FDR passive copper direct-attach cable (DAC) with QSFP+ connectors on both ends. It is a fixed-length integrated assembly engineered to carry four 14 Gb/s lanes for an aggregate signaling rate of 56 Gb/s using 64b/66b encoding. The 670759-B21 is HP's spare/option part number for the FDR-class QSFP-to-QSFP copper interconnect supplied with HP ProLiant, Apollo, and Cluster Platform InfiniBand kits. Because it is fully passive (no retimer, no laser, no electronics in the connector body), it adds zero PHY latency and zero power draw beyond the host-side SerDes. This is not an active optical cable (AOC), not a transceiver-plus-fiber assembly, not an Ethernet-only DAC, and not a breakout/splitter cable. Supplied by T.E.S IT-SOLUTIONS as a refurbished unit — bench-tested for link integrity, BER, and connector retention before shipment.

Specifications

OEM: HP (Hewlett Packard) — HP option / spare part
Manufacturer Part Number (MPN): 670759-B21
Cable Class: Passive Copper Direct-Attach Cable (DAC)
Protocol: InfiniBand FDR (IBTA) — single protocol, not VPI
Aggregate Rate: 56 Gb/s (4 lanes × 14 Gb/s, 64b/66b)
Length: 0.5 m (fixed, non-extendable)
Connectors: QSFP+ to QSFP+ (1-to-1, both ends identical)
Form Factor: SFF-8436 QSFP+ housing, copper twinax pairs
Power Draw: 0 W (passive, no electronics)
Latency: Cable-only propagation, no PHY processing
Backward Compatibility: Negotiates down to QDR (40 Gb/s) on legacy ports
Condition: Refurbished — tested by T.E.S IT-SOLUTIONS


What This Is NOT
This is not an EDR (100 Gb/s), HDR (200 Gb/s), or NDR (400 Gb/s) cable — its SerDes envelope is FDR. Plugging the 670759-B21 into an EDR or HDR port will negotiate the link down to FDR at best, or fail to train if the host enforces a minimum rate. It is not an Ethernet cable — although the QSFP+ form factor is shared with 40GbE DACs, this assembly is HP-keyed for InfiniBand FDR and is not validated as a 40GbE / 56GbE Ethernet interconnect. It is not an AOC — there is no laser, no fiber, no electronics; reach is limited by copper signal integrity. It is not a 1-to-2 or 1-to-4 splitter — both ends are full-rate QSFP+. It is not a generic / unbranded DAC — the cable carries HP's option-part EEPROM and is recognized by HP iLO and HP InfiniBand utilities as a qualified part.

Compatibility & Constraints
The 670759-B21 is the natural pairing for FDR-class InfiniBand fabrics built on Mellanox ConnectX-3 Pro (MCX354A-FCBT, MCX353A-FCBT) and early ConnectX-4 VPI adapters operating in FDR mode, terminated into Mellanox SX6036 / SX6506 / SX6512 FDR switches and the corresponding HP 4X FDR InfiniBand switch modules for the BladeSystem c-Class enclosure. At 0.5 m it is sized for intra-rack server-to-ToR or chassis-internal hops where bend radius and airflow density matter; it is too short for inter-rack runs. Because the cable is fully passive, both ends must be plugged into ports capable of driving QSFP+ FDR SerDes — passive copper at FDR has a practical reach ceiling of ~3 m, so this assembly is well inside the comfortable margin. HP-branded EEPROM is honored by HP servers (HP iLO will not flag a third-party warning) and by Mellanox switches; some non-HP / non-Mellanox switches may require MSA-compliant cable verification or an unqualified-optic override. For longer FDR reach (5 m and beyond) use FDR AOCs; for higher rate fabrics (EDR/HDR/NDR) the cable must be replaced with a rate-matched assembly.

Frequently Asked Questions (FAQ)
Q. What is the maximum data rate of the HP 670759-B21 cable?
The HP 670759-B21 operates at InfiniBand FDR — an aggregate of 56 Gb/s carried on four lanes of 14 Gb/s each with 64b/66b encoding. This is the maximum supported rate; the cable will not negotiate at EDR, HDR, or NDR.
Q. Can the HP 670759-B21 be used for 40 GbE or 56 GbE Ethernet?
No. The 670759-B21 is HP-keyed as an InfiniBand FDR cable. Although the QSFP+ connector form factor is physically shared with 40 GbE / 56 GbE DACs, this assembly is not qualified as an Ethernet interconnect and may be rejected or flagged by Ethernet switches that enforce MSA cable typing.
Q. What condition is the HP 670759-B21 supplied by T.E.S IT-SOLUTIONS?
The HP 670759-B21 is sold as refurbished by T.E.S IT-SOLUTIONS (tes-itsolutions.com). Every cable is bench-tested for link training, bit-error rate, and connector retention before shipment, with 1–3 business day handling and global express options.

Why buy from T.E.S IT-SOLUTIONS
T.E.S IT-SOLUTIONS is a Europe-based data-center hardware specialist serving HPC, AI, and enterprise procurement teams since 2007. Every refurbished InfiniBand cable ships only after live link-training verification against the matching speed grade — FDR cables are tested end-to-end on Mellanox FDR switching to confirm both connector EEPROM read and clean signal margin. We provide free pre-sale consultation on fabric speed planning, mixed-generation FDR/EDR/HDR migration paths, and HP / Mellanox / NVIDIA HCL alignment. Multi-currency B2B invoicing, EU stock with worldwide DHL / FedEx / UPS dispatch, and direct technical contact with our engineering team — not a call-center.