USB Type-C Explained

[actuallyinaus]

Hi all. The technical details for type-c are not very obvious and haven not been explained very well so here is a simple explanation for everyone to see the true power of type-c.

With a USB 3.1 10GB/s capable computer a single type-c port has 40GB/s of bandwidth and thus can do:

• Displayport 1.3 (at half bandwidth so limited to 4K 60hz) + 10GB USB upstream + 10GB USB downstream + USB 2.0
  
  • USB-C to USB-C
  • see quote 1 and image 2
• Displayport 1.2a (4K 60hz at 30bit color) + USB 2.0
  
  • USB-C to USB-C
  • see quote 2 and image 1
• Displayport 1.2a (4K 60hz at 30bit color)
  
  • USB-C to displayport cable or adapter
  • see image 3
• Displayport 1.3 (full bandwidth so 5K and even 8K) + USB 2.0
  
  • USB-C to USB-C
  • see quote 3 and image 1
• Displayport 1.3 (full bandwidth so 5K and even 8K)
  
  • USB-C to displayport cable or adapter
  • see image 3
• HDMI 2.0 (NOT HDMI 1.4) or DVI or VGA (no usb 2.0)
  
  • active adapters only (if needed they can get power from the Vconn pin)
  • see quote 4 and image 4

What about power? "furthermore, USB power delivery according to the newly expanded USB-PD 2.0 specification is possible at the same time." - wikipedia "along with all of the regular DisplayPort features a Type-C cable also carries the standard USB 2.0 interface and USB power, which always coexist alongside alt mode. So even in these configurations Type-C allows dedicated high power" - anandtech

NOTE: The macbook only suports USB 3.1 at 5GB/s

• so 20GB/s total bandwidth
• it's most likely that the displayport is running in 2.7GB/s mode across four channels which means full displayport 1.2 is not being met - hence probably can only do 4k at 30fps

How this is possible:

• FOUR data lanes
• USB 2.0 are separate pins
• power are separate pins

Quotes:

• [1] "By leveraging USB Type-C’s flexibility, the DisplayPort Alt Mode can choose to transmit on just one or two of the four available lanes, so that the other two lanes can be used for SuperSpeed USB data at the same time. In a docking station connection, for example, the use of two lanes for DisplayPort at 8.1 Gbps per lane would allow simultaneous transfer of SuperSpeed USB data (up to 10 Gbps in each direction) while also supporting a 4K UHD (3840 x 2160) DisplayPort monitor." - VESA
• [2] "Using 5.4 Gbps across all four high-speed lanes will support up to 4K (4096 x 2160) display resolutions at a 60Hz frame rate with up to 30-bit color." - VESA
• [3] "When using all four lanes for DisplayPort Alt Mode, which could drive a monitor with up to 5K (5120 x 2880) resolution, USB 2.0 data can still be carried across the USB Type-C connection using separate pins dedicated for that function." - VESA
• [4] "This also means that since DP Alt Mode is such a complete implementation of DisplayPort, that DisplayPort conversion devices will work as well. DisplayPort to VGA, DVI, and even HDMI 2.0 adapters will all work at the end of Type-C connection, and the VESA will be strongly encouraging cable makers to develop Type-C to HDMI 2.0 cables (and only HDMI 2.0, no 1.4) to make Type-C ports usable with HDMI devices." - anandtech

Sources:

• VESA
• Anandtech

Image 1: How FULL displayport is sent over the pins WITH USB 2.0:

Image 2: How HALF displayport is sent over the pins along WITH USB 3.1:

Image 3: How FULL displayport is sent over the pins WITHOUT USB 2.0:

Image 4 - HDMI 2.0 only or DVI or VGA (no USB 2.0):

Image 5 - Summary:

What about dual 4k monitors?

• Displayport 1.3 (at half bandwidth so limited to 4K 60hz) + Displayport 1.3 (at half bandwidth so limited to 4K) + USB 2.0
  • USB-C to USB-C
  • this might be possible through a dock - however I can't find any source to confirm this, it probably depends on the computer's wiring

 

[totten76]

Does that last diagram mean that if I had a monitor that gets plugged into the wall, and then connected it to the USB-C port, it could theoretically charge the laptop while doubling as a monitor?

 

[actuallyinaus]

Does that last diagram mean that if I had a monitor that gets plugged into the wall, and then connected it to the USB-C port, it could theoretically charge the laptop while doubling as a monitor?

Yes. This is why i expect the new apple display to have a usb-c port on it (though it might have TB and others as well).

In image 1 you can see the device-to-device power pins (Vbus) are free to be used simultaneously. The power pins are never re-purposed for any data transfer.

If the monitor takes the type-c cable directly then it could act as a hub allowing USB 2.0 (possibly USB 3.1 depending on what resolution you are running) and power all through the one cable, simultaneously.

"In a full (4 lane) DisplayPort configuration, along with all of the regular DisplayPort features a Type-C cable also carries the standard USB 2.0 interface and USB power which always coexist alongside alt mode,. So even in these configurations Type-C allows dedicated high power and USB 2.0 functionality, something the DisplayPort physical layer itself is not capable of." - anandtech

You can see a dock example here, PD stands for "USB Power Delivery" (that's the up to 5A 20V (100W) stuff)

Of course it it was a monitor it would be using some of the lanes for display instead of USB 3.1 or the pcie bridge.

 

[gordoabc]

It seems to me that given the MacBook spec states it can support UHD resolution we can expect to see a Thunderbolt Display replacement based on USB-C. It would be a 21.5 inch monitor which meets retina 220 ppi spec at UHD resolution which works via Displayport 1.2 native on the USB-C connector. It would provide power back to MacBook and use the USB 2 pins for FaceTime camera and sound. The USB 3.1 gen 1 (aka USB 3.0) would service a series of USB 3 ports on the back of display via hub.

 

[rekhyt]

Hi all. The technical details for type-c are not very obvious and haven not been explained very well so here is a simple explanation for everyone to see the true power of type-c.

With a USB 3.1 10GB/s capable computer a single type-c port has 40GB/s of bandwidth and thus can do:

• Displayport 1.3 (at half bandwidth so limited to 4K 60hz) + 10GB USB upstream + 10GB USB downstream + USB 2.0
  
  • USB-C to USB-C
  • see quote 1 and image 2
• Displayport 1.2a (4K 60hz at 30bit color) + USB 2.0
  
  • USB-C to USB-C
  • see quote 2 and image 1
• Displayport 1.2a (4K 60hz at 30bit color)
  
  • USB-C to displayport cable or adapter
  • see image 3
• Displayport 1.3 (full bandwidth so 5K and even 8K) + USB 2.0
  
  • USB-C to USB-C
  • see quote 3 and image 1
• Displayport 1.3 (full bandwidth so 5K and even 8K)
  
  • USB-C to displayport cable or adapter
  • see image 3
• HDMI 2.0 (NOT HDMI 1.4) or DVI or VGA (no usb 2.0)
  
  • active adapters only (if needed they can get power from the Vconn pin)
  • see quote 4 and image 4

What about power? "furthermore, USB power delivery according to the newly expanded USB-PD 2.0 specification is possible at the same time." - wikipedia "along with all of the regular DisplayPort features a Type-C cable also carries the standard USB 2.0 interface and USB power, which always coexist alongside alt mode. So even in these configurations Type-C allows dedicated high power" - anandtech

NOTE: The macbook only suports USB 3.1 at 5GB/s

• so 20GB/s total bandwidth
• it's most likely that the displayport is running in 2.7GB/s mode across four channels which means full displayport 1.2 is not being met - hence probably can only do 4k at 30fps

How this is possible:
Image

• FOUR data lanes
• USB 2.0 are separate pins
• power are separate pins

Quotes:

• [1] "By leveraging USB Type-C’s flexibility, the DisplayPort Alt Mode can choose to transmit on just one or two of the four available lanes, so that the other two lanes can be used for SuperSpeed USB data at the same time. In a docking station connection, for example, the use of two lanes for DisplayPort at 8.1 Gbps per lane would allow simultaneous transfer of SuperSpeed USB data (up to 10 Gbps in each direction) while also supporting a 4K UHD (3840 x 2160) DisplayPort monitor." - VESA
• [2] "Using 5.4 Gbps across all four high-speed lanes will support up to 4K (4096 x 2160) display resolutions at a 60Hz frame rate with up to 30-bit color." - VESA
• [3] "When using all four lanes for DisplayPort Alt Mode, which could drive a monitor with up to 5K (5120 x 2880) resolution, USB 2.0 data can still be carried across the USB Type-C connection using separate pins dedicated for that function." - VESA
• [4] "This also means that since DP Alt Mode is such a complete implementation of DisplayPort, that DisplayPort conversion devices will work as well. DisplayPort to VGA, DVI, and even HDMI 2.0 adapters will all work at the end of Type-C connection, and the VESA will be strongly encouraging cable makers to develop Type-C to HDMI 2.0 cables (and only HDMI 2.0, no 1.4) to make Type-C ports usable with HDMI devices." - anandtech

Sources:

• VESA
• Anandtech

Image 1: How FULL displayport is sent over the pins WITH USB 2.0:
Image

Image 2: How HALF displayport is sent over the pins along WITH USB 3.1:
Image

Image 3: How FULL displayport is sent over the pins WITHOUT USB 2.0:
Image

Image 4 - HDMI 2.0 only or DVI or VGA (no USB 2.0):
Image

Image 5 - Summary:
Image

What about dual 4k monitors?

• Displayport 1.3 (at half bandwidth so limited to 4K 60hz) + Displayport 1.3 (at half bandwidth so limited to 4K) + USB 2.0
  • USB-C to USB-C
  • this might be possible through a dock - however I can't find any source to confirm this, it probably depends on the computer's wiring

Great post, could mean that the upcoming 14" MBP will have 2-3 (possibly 4 if Apple's feeling generous) USB 3.1 Type-C ports and make it a lot thinner (but at the same time, powerful).