T420 Dock with USB 3.0

[CoolRunnings]

Does anyone know if the dock that has a USB 3.0 port on it will give a T420 USB 3.0 capabilities or will the USB 3.0 port perform at USB 2.0?

[jayton4]

The T420 will use the ports at USB 2.0 speeds. The laptop has to already have USB 3.0 in the chipset for the dock to work, and Intel didn't start including USB 3.0 in the chipsets until Ivy Bridge.

[dr_st]

According to this thread, it may actually work even if the USB3 controller is a separate chip. This has been verified for X220. However, the T420 has no USB3 controller at all, and the dock is just a passthrough. So as jayton4 says, it will work as USB2.

[jayton4]

According to this thread, it may actually work even if the USB3 controller is a separate chip.

That is an interesting post, I have been following it, too. I have yet to come across a USB 3.0 dock yet so that I can test it with my T420s that has the Renesas USB 3.0 controller.

[ansible212]

Certain Sandy Bridge ThinkPads had USB 3.0, including the Core i7 X220s and (I believe) all T420s.

The USB 3.0 port on the Mini Dock Series 3 with USB 3.0 therefore functions as such on my i7 X220. On ThinkPads without USB 3.0 my assumption (from what I've read) is that the USB 3.0 port on the Mini Dock would be in effect a USB 2.0 port.

My post in the linked thread was in the context of an earlier post in that thread to clarify the situation in respect of USB 3.0 equipped Sandy Bridge era ThinkPads (although my comments equally only applied to the i7 X220).