USB3-SATA-U3 prevents MacPro with El Capitan from starting up

USB3-SATA-U3 with ASMedia ASM1051e Chipset. MacOS 10.11 (El Capitan) on Macintosh Pro will not start up if the Plugable dock is plugged in - even if the dock is not powered on. Once the USB cable is unplugged from the dock the MacPro boots up fine.
The same MacPro had been working just fine with this dock before the update to El Capitan. Booting the MacPro from its backup Yosemite partition with the dock plugged in still works fine.

Here is a photo of the startup crash:

That’s quite strange. With the dock off I’m not sure how this would happen.

Have you tried moving the dock to a different USB port?

I will try that when I am able to reboot into 10.11. The MacPro has 5 built-in USB ports and it has a PCI card that adds 4 more. Every port is occupied at the moment.

Definitely try connecting to a built in port, we’ve seen some issues with add in cards with some of the latest OS X builds!

Before I posted the initial question I had been able to repeat 3 times that the crash shown happened when the USB3-SATA-U3 was plugged in and did not happen when it was unplugged.

Then the next day 10.11 booted fine with the USB3-SATA-U3 plugged in - over and over again, so the USB3-SATA-U3 is cleared of all wrongdoing.
It is plugged into a powered USB port on the monitor. I will get a longer USB cable to plug it directly into a native USB-2 port to test.
I’m now looking into replacing the USB-2 PCI card with a Sonnet USB-3 card to be able to make use of the Pluggable Dock’s speed.

I seems the Mac Pro now almost always gives this crash if the Yosemite partition is selected in Startup Disk and I use the Option key on startup to select the El Capitan partition, but a few days ago it was only when the USB3-SATA-U3 was plugged in.

Thanks for the update. Sorry to hear about those crashes! I’d recommend starting off by using Disk Utility to check for errors on the drive.

The Sonnet card should work well to increase speeds to our dock.

The drive has had Disk Utility run on it about a half dozen times this week. [We’re having a problem with Parallels Desktop on the Yosemite partition so their techs remoted in and among other things ran Verify Disk and Repair Permissions three times each and all was fine. The issue has now been kicked up to Engineering…]

Glad you think the Sonnet card will work with the dock. I’ll add it to my TBD list for when I’m gainfully employed again.