All iPhone 15 Models Support DisplayPort for Up to 4K HDR Video Output to External Display

That awkward moment when the A16 Bionic has a displayport controller connected to it that can do 8.64Gbps to do 4k 30Hz HDR but only a 480Mbps USB 2 controller.

For the base 15 & 15 Plus, how can a 4K/60 display be supported on a USB-C port that is limited to USB 2 speeds?

The USB Type-C connector allows for up to four high-speed differential pairs, which can be allocated to different protocols. For example, you could implement 5Gbps or 10Gbps SuperSpeed USB using two of the pairs and use the other two for dual-lane DisplayPort. Alternatively, you could have all four pairs used for quad-lane DisplayPort to drive high-resolution or high refresh rate displays.

Notably, there are dedicated USB 2.0 data lines on the USB Type-C connector that are always available, no matter the configuration of the high-speed differential pairs.

So in this case Apple just had to connect their existing USB 2.0 interface to those dedicated pins and run the new DisplayPort interface to the high-speed differential pairs.
For the 15 Pro models, it may actually more complicated since they might need to add multiplexers to switch the differential pair lines between the SuperSpeed interface and the DisplayPort interface as appropriate.

This picture shows the USB Type-C pinout. The blue TX and RX pins are the high-speed differential pairs, and the green D+/D- pins are the USB 2.0 lines.

Ok, serious question: is it becoming possible to use the iPhone Pro as a sort of desktop computer?

Think about it: A17 Pro chip, 8GB Ram, up to 1TB storage, USB 3 speeds... hook it up to a 4k display, with a USB-C hub you could also use a wired keyboard + mouse while charging the device.

I've been dreaming of the 1-device-for-everything solution for a while. I think specs-wise, we're almost there. The only thing we'd still need would be support for custom display resolutions, and better mouse support.

The capability is here now for Stage Manager on the iPhone. It would be awesome to plug an iPhone into a monitor and connect a mouse and keyboard to use it like an iOS desktop. Apple would probably lose a lot of iPad and Mac sales which is why I’m sure we don’t have this now, but hopefully we get it in the near future.

For the base 15 & 15 Plus, how can a 4K/60 display be supported on a USB-C port that is limited to USB 2 speeds?

Because DisplayPort is not USB. DisplayPort is DisplayPort.

USB Type-C is the connector. USB 2 is the protocol.

DisplayPort leverages the Alternate Mode Functional Extension of the USB Type-C interface, and shares similar electrical characteristics with USB 3.1, allowing use of common system elements.

* 4K @60Hz 24-bit color (without compression) with simultaneous USB 3.1
* 5K (5120 x 2880) display support without compression with simultaneous USB 2.0

Granted, it is still a dick move by Apple. The spec clearly supports simultaneous USB 3.1 with DP 4K@60. Apple is just deliberately deprecating down to USB 2.0 bc they want you to buy the Pro.

Approved.
I love this calm before the storm time between keynote and Friday’s pre-order opening. Where features slowly trickle out, things begin to take greater shape, make a little more sense. lrefect example of the sum being greater than its parts unfolding.