Foldable PCI Express Extender Assemblies Streamline Connections in High-Performance Computing

Bandwidth and data rates demanded by computing applications have grown year over year for over a decade. In leading sectors, bandwidth demand has been shown to double approximately every three years. This is driven by the 45% compound annual growth rate (CAGR) among providers of telecommunications services, cloud computing services, and information technology, especially in the banking, securities, and insurance sectors. In addition, artificial intelligence (AI) companies based on large language models (LLMs) continue to expand their operations. Industrial automation, including AI-aided inspection and autonomous vehicles, is also contributing to the demand for increased bandwidth and faster data speeds.

The infrastructure to supply high-speed data to these applications includes both wired and wireless networks. But within the hardware in high-performance computing (HPC), high-speed test equipment, and gaming, the connections between central processors and peripherals must also support ever-increasing data rates.

The power of PCIe

Networked devices or components connected to a central processor need a streamlined way to quickly and accurately transmit data, namely a peripheral component interconnect (PCI) technology. Diverse computing market segments, including servers and data centers, automotive and industrial, and workstations and hand-held devices, use the point-to-point serial architecture of PCI Express (PCIe) to ensure fast and reliable data transfer.

PCI-SIG, or Peripheral Component Interconnect Special Interest Group, is a consortium of approximately 900 member companies responsible for developing and managing the open industry standards for PCIe technology (Figure 1).

Figure 1: PCI-SIG’s specifications for PCI connectivity components have supported a continuous increase in data rates since 2003. (Image source: PCI-SIG)

The organization published PCIe 1.0 in 2003 to support 2.5 gigatransfers per second (GT/s), which met the needs of the 3G wireless standards in place at that time. Subsequent updates paved the way for year-over-year increases in I/O throughput while ensuring backward compatibility. For example, devices built to the PCIe 5.0 specification can reach 32.0 GT/s per lane, compatible with the 5G networking required for streaming and edge computing.

The low latency required for AI and edge processing, industrial automation, test equipment, and gaming is supported by these higher throughputs. The point-to-point architecture of PCIe technology also supports power-efficient performance, a key consideration for advanced computing applications.

Keeping HPC components cool

Even with the improved data rates and power efficiency supplied by the most current PCIe technology, HPC applications like real-time financial fraud detection, AI LLM systems, and computational fluid dynamics (CFD) need multiple parallel processors. Meeting this need while managing heat and space constraints is no easy task, especially when data cables connecting components and processors compete for space with avenues needed for air flow.

In such situations, designers of HPC installations turn to flat, foldable PCIe extender assemblies like those in 3M’s 8KDx series (Figure 2).

Figure 2: 3M’s 8KDx series PCIe 5.0 extender assemblies are thin, flexible cables that fold back on themselves. (Image source: 3M)

The 8KDx series is designed to the PCIe 5.0 standard and is backwards compatible with systems designed to earlier PCIe standards. They come in x8 and x16 versions with eight and sixteen conductor wires, respectively. Straddle-mount and surface-mount (SMT) terminations are available.

The silver-plated 30 AWG conductor wires are precision placed within a continuously laminated shield for an overall thickness of 0.74 mm. Compared to traditional wires, in which pairs of conductors are longitudinally wrapped in a spiral shield, 8KDx series extenders are thinner and less stiff. The more flexible design allows multiple PCIe extenders to be bundled and folded together without blocking critical airflow (Figure 3).

Figure 3: Continuously laminated, precision-placed 30 AWG conductors allow the 8KDx series to connect components without blocking air flow. (Image source: 3M)

Synchronizing high-speed test equipment

While HPC applications rely on parallel processing to handle large data sets, high-speed test equipment must connect processors, signal generators, graphics cards, and other peripherals such as oscilloscopes. These systems need synchronized signals and low latency to ensure valid test data.

The synchronization of signals to a single clock or the synchronization of multiple clocks is supported by PCIe 3.0, 4.0, and 5.0 standards. Technology built to these standards, like the 8KDx series, relies on 128b/130b encoding. In this encoding protocol, packets contain 128 bits of information bounded by 2 bits marking the start and end of the packet. The start and end bits permit clock synchronization and error detection, freeing the rest of the bits in the packet for data transmission.

8KDx series PCIe extenders use conductors with an 87 ±5 Ω impedance to further ensure data speed and integrity. The conductors minimize impedance mismatch and signal reflection when connecting with the baseline 85 Ω impedance of systems built to PCIe 3.0, 4.0, and 5.0 standards.

In addition, test engineers can confidently take advantage of 8KDx series assemblies’ flexibility and space-efficient design. Tests have shown no degradation of signal integrity when the cables are folded back upon themselves when compared to unfolded cables (Figure 4).

Figure 4: Signal integrity tests showed no increased loss in 8KDx series PCIe extenders when they are folded up to five times. (Image source: 3M)

Bringing glamour to gaming

Synchronization and low latency are also paramount in high-performance gaming setups. Often custom built, these setups connect a central processor to a graphics processing unit (GPU), a sound card, and an Ethernet card for internet connectivity, preserving a high data rate and clock synchronization in every connection. To achieve this, those building custom gaming setups turn to 8KDx series PCIe 5.0 extenders (Figure 5).

Figure 5: 8KDx series PCIe extender assemblies provide low-latency, synchronized connections among components in custom gaming rigs. (Image source: 3M)

8KDx series PCIe extenders can also help gaming rig designers manage the heat generated by the high-performance processors and peripherals. In addition to their low profile and flexibility, the extenders also come in a variety of cable lengths. Standard lengths are 0.25 m and 0.5 m, but 0.125 m, 0.75 m, and 1 m are readily available. Additionally, custom lengths, folds, and terminations can be developed in partnership with 3M. Gaming rig designers take advantage of 8KDx extenders’ available lengths, flexibility, and streamlined design to enhance the aesthetics of custom gaming rigs, an important part of gaming culture (Figure 6).

Figure 6: 8KDx series PCIe extender assemblies contribute to the aesthetics of gaming rigs while enabling high-speed data transfer and heat management. (Image source: 3M)

Conclusion

High-performance computing, high-speed test, and custom gaming applications all require high-speed data transfer, low latency, and high signal integrity. At the same time, space is often at a premium for these applications, making cable routing and heat management a challenge. The flexible, foldable 8KDx series of PCIe 5.0 extender assemblies combine power-efficient, synchronized data transfer at speeds up to 64 GT/s while maximizing space utilization and air flow.