都是C口 雷电3、雷电4、USB 3.0、USB 4有何区别？
最近关于苹果明年为iPhone换用USB-C接口的消息甚嚣尘上，看起来，一根线走天下的方便指日可待了。不过，你是否有疑惑，虽然都是USB-C接口，但实际上它可以对应雷电4、雷电3、USB 3.0、USB 4等多种协议，那么这之间到底有何区别呢？
虽然雷电4依然是40Gps带宽（双向），可PCIe链路从雷电3的16Gbps增加为32Gbps，且必须支持双4K或者8K显示输出，还支持四口雷电扩展坞、从睡眠唤醒以及虚拟机的Intel VT-d DMA（直接内存访问）保护，所以不要单纯从带宽，认为雷电3到雷电4只是换马甲。
相较而言，USB 3/DP、USB 4比雷电就宽容得多，跑不满40Gbps同样可以叫USB 4（非全功能），最小供电也分别只有4.5W和7.5W。
USB最早可以追溯到1996年，发起者包括微软、IBM、Intel等，目的很简单，就是为了推广一种通行接口。当时起步速率是1.5Mbps，USB 1.1升级到12Mbps，2001年，USB 2.0带宽飞跃，来到480Mbps，20年后的今天，USB 2.0依然活跃在各种领域。
2011年，USB 3.0横空出生，正式进入千兆时代，USB 3.0初始速率就达到了5Gbps。2014年，USB 3.1问世，其中USB 3.1 Gen2首次引入Type-C接口，速率提升到10Gbps。2017年，USB 3.2再次将速率提高到20Gbps，且C口成必须。
不过，2019年，USB组织启用新的命名机制，USB 3.0/3.1改名USB 3.2 Gen1/Gen2，USB 3.2则更名USB 3.2 Gen2x2，只是一些硬件厂商仍习惯与之前的命名习惯。
雷电3则整合了PCIe 3.0、DP1.2和USB 3.1与一体，支持4K 60/5K屏幕，100W供电，基于雷电3，外接显卡正式成为可能。
In fact, through an official picture, we can get a general idea:
If it has to be divided into three, six or nine classes, then the Lightning 4 certified interface and data line is undoubtedly the pearl on the crown, it is compatible with all previous lightning standards, and can achieve single-line transmission of up to 2 meters, including PCIe, DP, USB data and so on.
Although Lightning 4 still has 40Gps bandwidth (bi-directional), the PCIe link can be increased from 16Gbps of Lightning 3 to 32Gbps, and must support dual 4K or 8K display output, as well as four-port lightning docking, wake-up from sleep, and Intel VT-d DMA (direct memory access) protection of virtual machines, so don’t just change the vest from Lightning 3 to Lightning 4.
In comparison, USB 3/DP and USB 4 are much more tolerant than lightning. Dissatisfied 40Gbps can also be called USB 4 (non-full function), and the minimum power supply is only 4.5W and 7.5W respectively.
History of USB
USB can be traced back to 1996, the sponsors include Microsoft, IBM, Intel and so on, the purpose is very simple, is to promote a common interface. At that time, the starting rate was 1.5Mbps USB 1.1 upgrade to 12Mbps, in 2001, the bandwidth of USB 2.0 leapfrogged, and 20 years later, USB 2.0 is still active in a variety of fields.
In 2011, USB 3.0 was born across the sky and officially entered the gigabit era, and the initial rate of USB 3.0 reached 5Gbps. In 2014, USB 3.1 was introduced, in which USB 3.1 Gen2 introduced the Type-C interface for the first time, increasing the speed to 10Gbps. In 2017, USB 3.2 increased the speed to 20Gbps again, and the C port became a must.
However, in 2019, the USB organization launched a new naming mechanism, and USB 3.0 USB 3.1 changed its name to USB 3.2 Gen1/Gen2,USB 3.2 and changed its name to USB 3.2 Gen2x2, although some hardware manufacturers are still used to the previous naming habits.
In the same year, USB 4 was released as a civilian version of Lightning 3, with bandwidth increased to 40Gbps and power supply increased to 100W, introducing support for PCIe links and DP1.4a transmission.
History of Thunderbolt (“Thunder Lei”)
Developed jointly by Intel and Apple, Lightning made its debut as Light Peak in 2009 and was officially launched in 2011. It was developed based on miniDP at that time, and was designed to integrate the mixed output of traditional data and video signals, including the original daisy chain. The dual-channel bandwidth is 20Gbps. Two years later, Lightning 2 came out, upgraded to support DP1.2 signal transmission, supporting 4K for the first time.
Thunder 3 integrates PCIe 3.0, DP1.2 and USB 3.1 into one, supporting 4K 60max 5K screen and 100W power supply. Based on Lightning 3, an external graphics card is officially possible.