"Some USB 3 cards not working with El Capitan
Problems with Orico and CalDigit USB 3 cards have been reported in Apple Discussions. The problem may be limited to cards that require drivers. I have the first generation of the CalDigit USB3/eSATA card, and have seen the problem. First, it should be mentioned that there will be no driver fix for this older card. CalDigit has also removed a Yosemite driver from their downloads. I have the driver, and it seems to work, but I spend so little time in Yosemite that I can't vouch for there being no problems at all. So now the card works officially with Snow Leopard through Mavericks.

The second-Gen CalDigit USB3/eSATA card requires no drivers, has a minimum requirement of 10.8.2, and is reported to work with El Capitan.

The first-gen CalDigit card itself causes no problems in a clean El Capitan installation. It is simply non-functional. If you make the mistake of installing the CalDigit Yosemite (or presumably any earlier) driver, as I did when beta testing El Cap, you get stuck in an ugly, unending cycle of kernel panics and restarts. A similar result was reported in Apple Discussions. In that case, the information provided was sketchy, but I suspect that the person who posted had upgraded an existing system, so a CalDigit driver was already present. Long story short, if you have a USB 3 card installed, and it requires drivers, proceed with caution. Install El Cap clean rather than letting it upgrade an earlier OS that has drivers installed for the card.
-Kathryn"

Thanks Kathryn. In a later thread I saw info from a developer note on USB Changes in OS X 10.11:

... Changes to USB in OS X v10.11
• The USB stack is completely redesigned to increase stability and performance compared to Mac OS 10.10. Applications and third-party drivers for vendor-specific USB devices built with 10.10 SDK require no modification.
  
  
• Applications that use IOUSBLib APIs should continue to work with no modification. IOKit drivers that use IOUSBDevice and IOUSBInterface APIs should continue to load and be functional with no regressions.
  
  
• If you are developing a new IOKit driver that uses IOKIT USB APIs, please refer to the OS X v10.11 SDK for new API and classes such as IOUSBHostDevice and IOUSBHostInterface. New applications developed using the OS X v10.11 SDK should continue to use the IOUSBLib APIs.
  
  
• Different classes of USB devices should not exhibit any regression in functionality compared to the OS X v10.10 release.

"New in Release 346.03.02f02

Graphics driver updated for Mac OS X El Capitan 10.11 (15A284)

Contains performance improvements and bug fixes for a wide range of applications.

Includes NVIDIA Driver Manager preference pane.

Includes BETA support for iMac and MacBook Pro systems with NVIDIA graphics

Release Notes Archive:
This driver update is for Mac Pro 5,1 (2010), Mac Pro 4,1 (2009) and Mac Pro 3,1 (2008) users.
BETA support is for iMac 14,2 / 14,3 (2013), iMac 13,1 / 13,2 (2012) and MacBook Pro 11,3 (2013), MacBook Pro 10,1 (2012), and MacBook Pro 9,1 (2012) users. "

As of post date, the latest CUDA version is still CUDA 7.5.20 from Oct. 1st, 2015.
  

• How to create a bootable OS X installer
  
  
• Edit your photos using third-party extensions in Photos for OS X El Capitan
  
  
• If Share options or Markup is missing after upgrading to OS X Yosemite or El Capitan
  
  
• On Oct. 5th Apple revised docs on security content of OS X 10.11, iTunes 12.3, WatchOS 2, and iOS 9,

(Topic-based page of How-To, Troubleshooting & Tips for Mac/OS X/iOS Users.)