Intel Shares Details on Thunderbolt 4, Launching Later This Year

[canhaz]

Lastly, you'd would have really thought TB4 would have used PCIe 4.0 as that would make so much sense given the current timing and rollout. Why on earth release a new TB4 and use the old stuff?

This seems kind of rushed and not well thought out. Perhaps there's some behind the scenes stuff going on we don't know about. Like maybe USB4 influenced this decision.

 

[joevt]

Hmm that doesn't sound right. I'm using the new 2 meter Apple Pro TB3 cable.

According to Apple, it's an active TB3 cable that supports USB 3.1 Gen 2

View attachment 932204

Right. The Apple Pro cable is the first active cable with this capability - it might qualify as being a Thunderbolt 4 cable except no Thunderbolt 4 devices exist yet (except in testing) so Apple calls it a Thunderbolt 3 cable.

This honestly seems kind of theoretical though and still feels kinda confusing. Non-enthusiasts could quite easily get the wrong impression, as there's no reason to believe there will be much (if any) real world improvement in actual data rates. It really seems to be upping a requirement with little to no speed increase, yet trying to spin it as this shiny new thing.

A possible 10% increase in speed (2750 MB/s increased to 3000 MB/s) - theoretical maybe until normal people can test it, and not a big increase, but it's something.

Lastly, you'd would have really thought TB4 would have used PCIe 4.0 as that would make so much sense given the current timing and rollout. Why on earth release a new TB4 and use the old stuff?

This seems kind of rushed and not well thought out. Perhaps there's some behind the scenes stuff going on we don't know about. Like maybe USB4 influenced this decision.

Tiger Lake CPUs may have PCIe 4.0 and Thunderbolt 4. Whether PCIe 3.0 or PCIe 4.0 is used, Thunderbolt 4 is limited to 32 Gbps (4 lanes of PCIe 3.0 or 2 lanes of PCIe 4.0). Thunderbolt uses 20.625 Gbps per lane which is still faster than PCIe 4.0's 16 GT/s per lane. Increasing the bandwidth further is going to be more difficult than the previous increase. Maybe they could have done what VirtualLink did and use the USB 2.0 lines as a high speed duplex connection to add a third Thunderbolt lane.

You're right though. Thunderbolt has a total bandwidth of 40 Gbps (5 GB/s) but only 22 or 24 Gbps can be used by PCIe traffic. If the controller had more lanes (PCIe 3.0 x8) or higher bandwidth (PCIe 4.0 x4) then more PCIe data could be transmitted (maybe 4 GB/s) when no bandwidth is being used by DisplayPort.