Engineering: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] VirtualLink never launched successfully.
VirtualLink specifications
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]
| 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][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]
Implementation in graphics cards and devices
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]
Discontinuation & abandonment
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]
References
- ↑ "The next generation of VR headsets will connect over a single USB-C cable". The Verge. https://www.theverge.com/2018/7/17/17583362/virtuallink-vr-headsets-oculus-valve-microsoft-connect-usb-c-cable.
- ↑ "VirtualLink: Everything USB Type-C Is Supposed To Be". Forbes. 2018-08-17. https://www.forbes.com/sites/moorinsights/2018/08/17/virtuallink-everything-usb-type-c-is-supposed-to-be/.
- ↑ 3.0 3.1 3.2 3.3 Smith, Ryan (July 17, 2018). "VirtualLink USB-C Alt Mode Announced: Standardized Connector for VR Headsets". https://www.anandtech.com/show/13088/virtuallink-announced-standardized-connector-for-vr-headsets.
- ↑ "Virtual reality giants unveil VirtualLink as a standardized cable that may simplify VR rigs". PCWorld. https://www.pcworld.com/article/3290466/virtual-reality/virtual-reality-giants-unveil-virtuallink-as-a-standardized-cable-that-may-simplify-vr-rigs.html.
- ↑ "VirtualLink Removes Tangles from VR Goggles". EEJournal. 7 August 2018. https://www.eejournal.com/article/virtuallink-removes-tangles-from-vr-goggles/.
- ↑ "INFO: Hardware required for PSVR2 :: iVRy Driver for SteamVR PSVR2" (in en). https://steamcommunity.com/app/992490/discussions/17/3879344463500344882/.
- ↑ iVRy_VR (2023-09-28). "Author of the PSVR2 PC driver on Reddit". http://www.reddit.com/r/PSVR/comments/16tmzmz/no_usbc_on_gpu/k2jtxac/.
- ↑ Lang, Ben (20 August 2018). "GeForce RTX Cards Announced with VirtualLink VR Connector". Road to VR. https://www.roadtovr.com/nvidia-geforce-rtx-virtuallink-vr-connector/.
- ↑ "NVIDIA Unveils Quadro RTX, World’s First Ray-Tracing GPU". NVIDIA. https://nvidianews.nvidia.com/news/nvidia-unveils-quadro-rtx-worlds-first-ray-tracing-gpu.
- ↑ Smith, Ryan. "NVIDIA Announces the GeForce RTX 30 Series: Ampere For Gaming, Starting With RTX 3080 & RTX 3090". https://www.anandtech.com/show/16057/nvidia-announces-the-geforce-rtx-30-series-ampere-for-gaming-starting-with-rtx-3080-rtx-3090.
- ↑ Lang, Ben (2020-10-28). "AMD Announces Radeon RX 6000-series GPUs with USB-C "for a modern VR experience"". https://www.roadtovr.com/amd-radeon-rx-6900-xt-6800-xt-price-release-date-specs/.
- ↑ "Valve Cancels VirtualLink Adapter Accessory for Index, Cites Technical Issues & Laptop Adoption". RoadtoVR. https://www.roadtovr.com/valve-index-virtuallink-adapter-canceled/.
- ↑ Lang, Ben (2020-09-03). "The VirtualLink Single-cable VR Headset Connection Standard Has Been Abandoned" (in en-US). https://www.roadtovr.com/virtuallink-connection-standard-abandoned/.
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