So I got a brand new 2012 11" MBA with 2.0 GHz Core i7, 8GB RAM, 256 GB SSD. When attaching an external HDD I noticed that I only get a USB 3 connection when I plug the disk directly into one of the MBA's USB ports. As soon as I connect the disk to the MBA through a USB 3 hub the disk drops back to USB 2.
• I've used two different USB 3 hubs. The behavior is the same with both.
• I've used quality USB 3 cables for the hubs and the disks. No USB2-only cables were involved.
• The hubs also connected other USB 2 peripherals to the MBA. But removing all the USB 2 stuff didn't change anything.
• The HDD I was using was a 3.5" WD 1 TB disk installed in a USB 3 SATA dock. I changed to another USB 3 SATA dock from a different manufacturer, but the behavior was the same. No improvement.
•I checked USB 3 vs. USB 2 using Apple System Profiler, not by measuring transfer rates. Although the rates I saw were consistent with the reported protocol (~ 30 MB/s via USB 2, ~ 80 MB/s via USB 3 probably limited by the HDD and/or SATA-USB dock).
• The behavior was the same on both USB ports of the MBA.
So, can anybody tell me what's wrong here? Is my MBA's USB toast or is this some kind of weird thing in Apple's USB 3 driver? My understanding is that a USB 3 hub should ensure USB 3 speeds for all attached devices (as long as the host supports USB 3 obviously). I've never heard that you only get USB 3 speeds for devices attached directly to the host.
Thanks in advance for any insight and advice.
• I've used two different USB 3 hubs. The behavior is the same with both.
• I've used quality USB 3 cables for the hubs and the disks. No USB2-only cables were involved.
• The hubs also connected other USB 2 peripherals to the MBA. But removing all the USB 2 stuff didn't change anything.
• The HDD I was using was a 3.5" WD 1 TB disk installed in a USB 3 SATA dock. I changed to another USB 3 SATA dock from a different manufacturer, but the behavior was the same. No improvement.
•I checked USB 3 vs. USB 2 using Apple System Profiler, not by measuring transfer rates. Although the rates I saw were consistent with the reported protocol (~ 30 MB/s via USB 2, ~ 80 MB/s via USB 3 probably limited by the HDD and/or SATA-USB dock).
• The behavior was the same on both USB ports of the MBA.
So, can anybody tell me what's wrong here? Is my MBA's USB toast or is this some kind of weird thing in Apple's USB 3 driver? My understanding is that a USB 3 hub should ensure USB 3 speeds for all attached devices (as long as the host supports USB 3 obviously). I've never heard that you only get USB 3 speeds for devices attached directly to the host.
Thanks in advance for any insight and advice.
Last edited: