I understand that if I insert a USB 2.0 device into a USB 3.0 port on a mac the port will " lock" as 2.0 only.
Is it possible to revert this lock back to a 3.0 ?
iMac, OS X Mountain Lion (10.8.2)
Where did you hear that? I have never heard of anything like this. Can anyone confirm?
To revert back to USB 3, unplug the USB 2 device.
Allan
^ Yes, that's the impression I get from that article. The OP seemed to be implying that if you ever connect a USB2 device to a USB3 port, the port is permanently locked into USB2 even if you remove the USB2 device completely. That's not the case, is it?
But the OP has a point. From the KB article he linked to:
How do I get the best performance from the USB 3 ports?
The first device you plug in will configure the port, so always connect USB 3 capable hubs or devices first.
What happens if I plug in a USB 2 device into the USB 3 port first?
If you plug in a USB 2 hub first, all devices connected or "daisy-chained" to that hub will operate up to the maximum transfer rate of USB 2 speed (480 Mbps).
It does not directly say how to revert the port back to USB 2?
Not from anything I have read on the subkect.
Allan
Klaus, I think it's pretty clear - all that's needed to revert the port back to USB3 is to simply unplug all USB2 devices connected to it. Notice how the linked article says "If you plug in a USB2 hub FIRST...."
Just make sure that if you have a mix of USB3 and USB2 devices, connect the USB3 devices first and then the USB2 ones. Then the USB3 devices will run at USB3 speeds.
I think it's pretty clear
If you say so, but to me it is NOT clear from that KB article! 🙂
I picked this up from another forum, which did indicate the port was permantly locked to 2.0 if that was plugged in first. They reccomended a full re-install of the O/S. Hope not true & just as simple of switching a device back to a 3.0 device.
Please provide link.
That is not my understanding of USB 3.
Allan
^ That link doesn't work. It says "Domain not active".
You have to spell it like this:
http://forums.macrumors.com/showthread.php?t=1433387
It's macrumors, not macrumours.
As for the thread: The poster 'g4cube' says this: "Connect to a USB2 computer, you get USB2 performance. Connect to a USB3 computer, you get USB3 performance."
Doesn't say anything about a USB3 port having its USB3 ability being permanently destroyed or anything like that.
Read http://www.totalphase.com/support/kb/10047/
In this article it states that host detects the presents of low speed device on the bus by a pull-up resistor on D- line and high speed devices by a pull-up resistor on D+. So if the D- line is high during idle, the low speed is in effect.
It does NOT say anything about reboot only that the USB bus must go idle.
Allan
Fair enough, I assume the only final way is to try it !
If not an issue cannot see why apple support brought it up or macrumours.
Personally I thought that article was rather clear that the bus will revert to USB 3 as soon as the last USB 2 devices is removed and the bus goes idle again.
Allan
USB 3.0 locked as USB 2.0 ?
