VirtualLink

VirtualLink was a proposed USB-C Alternate Mode that was historically intended to allow the power, video, and data required to power virtual reality headsets to be delivered over a single USB-C cable instead of a set of three different cables as it was in older headsets.^[1][2] The standard was supported by Nvidia, AMD, HTC Vive, Oculus VR, Valve, and Microsoft.^[3] The VirtualLink Consortium was chaired by Rambo Jacoby representing Nvidia.^{[citation needed]}

According to its specifications, the VirtualLink cable consisted of:

• DisplayPort:
  • 4 × DisplayPort balanced pair data path
  • DisplayPort HPD (hot-plug detection pin) as a single wire.
  • DisplayPort AUX signal as a balanced pair
• USB 3.1 signals
  • A USB TX balanced pair for USB 3.0 data
  • A USB RX balanced pair for USB 3.0 data
• I2C wire to control the USB Billboard interface, in case the cable is plugged into an unsupported interface.
• VBUS carrying power to HMD visor
• GND ground

The USB-C plug pinout specified:^{[citation needed]}

Unlike most alt-modes this remapped A7, A6, B6, B7 to carry a USB 3.0 signal, instead of the usual passive USB 2.0 signal. This means that one would not be able to extend the cable using a standard USB-C 3.0 cable, which has these pins mapped only for unshielded USB 2.0 signals. Also this required the VirtualLink port to also detect the correct orientation of the USB-C plug to ensure that the USB 3.0 TX and RX lanes are correctly connected.

In VirtualLink mode, there were six high-speed lanes active in the USB-C connector and cable: four lanes transmit four DisplayPort HBR 3 video streams from the PC to the headset while two lanes implement a bidirectional USB 3.1 Gen 2 channel between the PC and the headset. Unlike the classic DisplayPort USB-C alternate mode, VirtualLink has no USB 2.0 channels active, instead providing a higher speed USB 3.1 Gen 2 (SuperSpeed+) over the same A6, A7, B7, B6 pins. VirtualLink also required the PC to provide 15 to 27 watts of power.^[3][4] No information pertaining to VirtualLink alternate mode compatibility with USB4 (and so Thunderbolt 3 alternate mode) had been published.

To achieve six high-speed lanes over USB-C, VirtualLink required special cables that conformed to version 1.3 of the USB-C standard and used shielded differential pairs for both USB 2.0 pairs.^[3][5]

The available bandwidth was estimated to be equivalent to DisplayPort 1.4 (32.4 Gbit/s, up to 4K @ 120 Hz with 8 bpc color) for video and 10 Gbit/s of USB 3.1 Gen 2 data.^[3]

As of March 2023 Sony PSVR2 has a single 5m USB Type-C cable connection to PS5 which seems to be working with Nvidia GeForce 20 series cards as well; because, unlike most ports, VirtualLink must also provide the required 12V via USB Power Delivery, an uncommon voltage, and they additionally support standard two-lane DisplayPort alt-mode, but the PSVR2 headset does not use the actual four-lane VirtualLink alt-mode, pinout or special shielded cable.^[6][7]

Nvidia GeForce 20 series cards, initially released in 2018, implemented a single VirtualLink port in all RTX Founders Edition (FE) cards (2060, 2070, 2080, 2080 Ti).^[8] This port was also made available on Quadro RTX cards.^[9]

As of Nvidia's GeForce 30 series cards announcement, all of Nvidia's new Founders Edition GPUs, alongside the partner boards announced so far, lacked a VirtualLink port due to its discontinuation.^[10] By contrast, the AMD Radeon RX 6000 series, announced in October 2020, implemented a VirtualLink port for the first time.^[11]

As of August 2020, the VirtualLink standard had failed to propagate into the virtual reality headset market. The Valve Index had initially developed a VirtualLink accessory, but it was canceled due to technical signaling and reliability issues.^[12] By September of that year, it had been abandoned by its consortium, and the website now redirects to its Wikipedia page.^[13]

• VirtualLink Consortium website
• http://www.virtuallink.org/