Hi Steve,
Thanks for posting the difficulty you experienced when trying to run 3DNA on Mac. A quick Google search with "Illegal instruction: 4 Mac" leads to the following link:
http://stackoverflow.com/questions/14268887/what-is-the-illegal-instruction-4-error-and-why-does-mmacosx-version-min-10What version of Mac OS X are you using? Click the Apple icon on the upper-left corner, and then click "About This Mac" to get the info. As I am posting this message, my MacBook Air has "Version 10.11.6". Please post your info back.
The distributed version of 3DNA v2.3 for Mac was compiled with Mac OS 10.8 on
SBGrid, which is more than 3 years old now. Since newer Mac OS X are free, so virtually all Mac users should be using newer versions than 10.8. I suspect yours may be older (10.6?). Certainly, you're the first one who's reported such an error message.
Alternatively, since 3DNA v2.3 is now distributed with source code, you could easily go to the src/ directory and type '
make'. Assuming you've the builder tools (Xcode/gcc) available on your Mac (which can compile the classic "Hello, World" C program), then everything should be alright. Have a try and let me know how it goes.
Xiang-Jun