The USB-C interface supports the function of DisplayPort (DP) signal transmission, which mainly relies on the DisplayPort Alt Mode technology. The popularization of this technology on laptops can be traced back to **2015 to 2016**, and the specific development process is as follows:
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1. **The launch and early application of technical standards (2015-2016)**
- **2015**: DisplayPort 1.4 standard was released, officially supporting video signal transmission through USB-C Alt Mode. This mode allows the USB-C interface to reuse its high-speed channels (such as TX/RX pins) to transmit DP signals, while being compatible with USB data transmission and PD fast charging.
- **2016**: Apple fully adopted the Thunderbolt 3 interface (based on the USB-C physical form) in the MacBook Pro for the first time. Thunderbolt 3 natively supports the DP1.2 protocol and can achieve 4K@60Hz video output through USB-C. This marks the first time that the USB-C interface has realized the DP signal transmission function in high-end notebooks.
- At the same time, other manufacturers began to follow suit. For example, the AOC P2 series monitors released in 2016 already support connecting to laptops via USB-C's DP Alt Mode to achieve the first-line screen projection function, which indirectly confirms that some laptops in the same period already support this technology.
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2. **Popularization of non-Thunderbolt interfaces (after 2017)**
- **2017**: Huawei introduced a USB-C interface (non-Thunderbolt protocol) supporting DP1.2 in the MateBook X Pro, becoming an early adopter of this technology in the Windows camp. This type of interface achieves video output through DP Alt Mode without relying on the high-cost main control chip of the Thunderbolt protocol.
- **2018-2019**: With the popularization of USB-C interfaces, more mid-to-high-end notebooks began to support DP Alt Mode. For example, HP introduced a USB-C interface supporting DP1.2 in the EliteBook 700 series on the AMD platform, covering more price ranges.
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3. **Technology optimization and mainstreaming (after 2020)**
- **Protocol openness and cost reduction**: In 2019, Intel opened the Thunderbolt 3 protocol and integrated the main control chip into the CPU, which indirectly promoted the USB-C interface's support for DP signals. At the same time, the launch of the USB4 standard (2020) further integrated Thunderbolt 3 and DP protocols, allowing more mid-range notebooks to support DP video output at a lower cost.
- **Bandwidth improvement**: The release of DP1.4 (2016) and DP2.0 (2019) further improved the video transmission capabilities of the USB-C interface. For example, DP1.4 supports 8K@60Hz output, while DP2.0 bandwidth can reach 80Gbps, promoting the application of USB-C in high-end creative notebooks.
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4. **Key difference: Thunderbolt interface vs. DP support of regular USB-C**
- **Thunderbolt interface**: Thunderbolt 3 (USB-C form factor) launched in 2015 natively supports DP protocol and has higher bandwidth (40Gbps), which can realize data transmission, video output and charging at the same time. Apple MacBook Pro (2016 model) is a typical example.
- **DP Alt Mode of regular USB-C**: Relying on DisplayPort Alt Mode technology, the bandwidth is determined by the USB version (such as USB3.1 Gen2 is 10Gbps). This type of interface is more common in non-Thunderbolt notebooks, such as Huawei MateBook series after 2017.
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Summary timeline
- **2015**: DP Alt Mode technology was released with DP1.4 standard, laying the foundation for USB-C video transmission.
- **2016**: Apple MacBook Pro was the first to realize USB-C DP function through Thunderbolt 3; other manufacturers began to test the waters.
- **2017-2019**: Non-Thunderbolt USB-C interfaces support DP Alt Mode and gradually become popular, covering mid-to-high-end notebooks.
- **After 2020**: USB4.0 and DP2.0 promote interface performance upgrades, support higher resolution and multi-screen expansion.
**2016 is a watershed year**:
**Almost all laptops launched before 2016 do not support DP signal output via USB-C**, mainly because the technical standard (DP Alt Mode) is not yet mature and the Thunderbolt 3 interface is not popular.
- **The first device to support DP Alt Mode**:
Apple's 2016 MacBook Pro is the first consumer-grade device to fully support Thunderbolt 3 (including DP function), while the DP support of ordinary USB-C interfaces is later (such as Huawei MateBook X Pro in 2017).
Through the above development, the DP signal transmission function of the USB-C interface has gradually become a standard feature of mid-to-high-end notebooks from being exclusive to high-end devices in 2016. Its technical core lies in the coordinated evolution of DisplayPort Alt Mode and Thunderbolt protocol.
