Record: why is there no lightning 4 interface graphics card docking station and mobile hard disk?

Thunder and lightning 4 After the interface is released ,intel Released at the same time 3 Lightning interface master chip , They are JHL8540、JHL8340、JHL8440.

among JHL8440 It is a chip for external expansion devices , But this time JHL8440 Only one is left PCIe3.0 The passage of , That is, only PCI3x1, from PCIe The theoretical speed can only reach 980MB/s（7.9Gbps）, There are still losses in actual use , So external expansion equipment manufacturers cannot use PCIe transfer M.2 NVMe Solid state and transit graphics card docking stations .

And in thunder and lightning 3 Time ,JHL7440 There is 4 strip PCIe3.0 namely PCIex4, The theoretical bandwidth can reach 32Gbps, So external device extension manufacturers can use them to transfer m.2 NVMe Solid state drive and graphics card docking station , So as to achieve high-speed bandwidth , But the problem is , Thunder and lightning 3 Bandwidth scheduling limits for , The most you can do is use 22Gbps ah .

So on the other hand , If you want to use it JHL8440 Manufacturing high bandwidth external expansion devices , What should be done ？ The answer is ： From the... On the motherboard JHL8540 Lightning of 4 The interface is connected to the external expansion device JHL8440 Thunder and lightning 4 Interface , And then from JHL8440 Lightning of 4 Interface to JHL7440 Lightning of 3 Interface （ Thunder and lightning 4 Downward compatible with lightning 3）, from JHL7440 Of PCIe3.0 x4 Transfer to an external expansion device .

What's the point of that ？ It can be directly from JHL8540 Lightning of 4 Interface to JHL7440 Lightning of 3 Interface , Therefore, manufacturers of these high bandwidth external expansion devices do not need to manufacture them directly , They have old thunderbolts 3 The equipment , For example, lightning 3 Interface graphics card docking station , Thunder and lightning 3 Mobile hard disk with interface .

Here is another question ,JHL8540 Have PCIe3.0 x4 Wiring of （ A pin used to communicate with the processor ）, Can you use JHL8540 Manufacturing lightning 4 Interface between the graphics card docking station and the mobile hard disk ？