VirtualLink

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VirtualLink is a discontinued USB-C alternate mode that was intended to allow the power, video, and data required to power virtual reality headsets to be delivered over a single USB-C cable and connector instead of 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]

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).[4] This port is also available on Quadro RTX cards.[5]

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.[6] By contrast, the AMD Radeon RX 6000 series, announced in October 2020, implemented a VirtualLink port for the first time.[7]

VirtualLink specifications[edit]

According to its specifications, the VirtualLink cable consisted of:

  • DisplayPort:
    • 4x 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]

A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1
GND DP[0]+ DP[0]− VBUS CC1 USBTX+ USBTX− DP[AUX]+ VBUS DP[3]− DP[3]+ GND
GND DP[1]+ DP[1]− VBUS DP[AUX]− USBRX− USBRX+ VCONN VBUS DP[4]− DP[4]+ GND
B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12

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][8] No information pertaining to VirtualLink alternate mode compatibility with USB4 (and so Thunderbolt 3 alternate mode) has been published, as of April 2019.

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][9]

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]

Discontinuation & abandonment[edit]

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.[10] By September of that year, it had been abandoned by its consortium, and the website had been redirecting to its Wikipedia page.[11]

References[edit]

  1. ^ "The next generation of VR headsets will connect over a single USB-C cable". The Verge.
  2. ^ "VirtualLink: Everything USB Type-C Is Supposed To Be". Forbes. 2018-08-17.
  3. ^ a b c d Smith, Ryan (July 17, 2018). "VirtualLink USB-C Alt Mode Announced: Standardized Connector for VR Headsets". AnandTech. Retrieved 2018-08-21.
  4. ^ Lang, Ben (20 August 2018). "GeForce RTX Cards Announced with VirtualLink VR Connector". Road to VR.
  5. ^ "NVIDIA Unveils Quadro RTX, World's First Ray-Tracing GPU". NVIDIA.
  6. ^ Smith, Ryan. "NVIDIA Announces the GeForce RTX 30 Series: Ampere For Gaming, Starting With RTX 3080 & RTX 3090". www.anandtech.com. Retrieved 2020-09-03.
  7. ^ Lang, Ben (2020-10-28). "AMD Announces Radeon RX 6000-series GPUs with USB-C "for a modern VR experience"". Road to VR. Retrieved 2020-11-09.
  8. ^ "Virtual reality giants unveil VirtualLink as a standardized cable that may simplify VR rigs". PCWorld.
  9. ^ "VirtualLink Removes Tangles from VR Goggles". EEJournal. 7 August 2018.
  10. ^ "Valve Cancels VirtualLink Adapter Accessory for Index, Cites Technical Issues & Laptop Adoption". RoadtoVR.
  11. ^ Lang, Ben (2020-09-03). "The VirtualLink Single-cable VR Headset Connection Standard Has Been Abandoned". Road to VR. Retrieved 2021-12-11.

External links[edit]