Molex Genesis SFF-TA-1040: Enabling the Next Generation of PCIe Internal Cabling Standards

Author: Adonis Nester, New Product Development Manager, Molex Collection: 2025 OCP Global Summit - Expo Hall Sessions

Summary

Molex presents Genesis, a direct-attach internal cable assembly designed from the ground up for PCI Express 7.0 at 128 Gbps per lane using PAM-4 signaling at 85 ohm nominal impedance, compliant with the SFF-TA-1040 standard. The product addresses four design pillars: Fast (128 Gbps PAM-4, exceeding PCI SIG spec limits for PCIe 7.0), Dense (under 9 mm mated right-angle cable exit height, one of the lowest profile solutions available), Flexible (28-32 AWG wire gauge compatibility, multiple cable exit orientations, modular pinouts), and Robust (fixed-pin top-mounted wafer design, 40N wrench testing, through-hole solder posts, recessed contacts for scoop-proofing).

The Genesis x8 standard offering is a 24 differential pair (DP), 74-pin design with common grounds between all pairs. Of the 24 DPs, 16 are dedicated to 8 TX and 8 RX data pairs, while the remaining 8 DPs serve sideband functions (REFCLK, FLEXIO, USB). The connector supports the M-XIO source connector pinout as defined in the OCP Base Specification v0.7, which is expected to be the mainstream configuration for Genesis x8 and x16. Use cases include ASIC-to-ASIC, ASIC-to-baseboard, ASIC-to-NIC, and cabled backplane connections. Direct-attach wire termination eliminates paddle card variability (no PCB/FR4 intermediate), reducing channel loss. Available configurations include x8 (28 mm width), x16 (47 mm), and planned x20 (57 mm). Simulated SI results show SDD21 insertion loss at 32 GHz of -3.4 dB at 250 mm, -5.3 dB at 500 mm, -7.2 dB at 750 mm, and -9.2 dB at 1000 mm cable length. A live demo ran at 128 Gbps with a Genesis x8 1200 mm cable assembly on a PCIe 7.0 chipset evaluation board using PRBS31 pattern at 32 dB loss channel. First-off samples use 29 AWG twin-ax; vertical and angled-exit versions planned for early next year. PCB Receptacle Series: 300988; R/A Cable Series: 300989.