Update README.md

README.md

@@ -74,7 +74,7 @@ Note that `launchctl` commands appear to not work correctly when run inside tmux
 
 ##Caveats
 
-DLite depends on [xhyve](https://github.com/mist64/xhyve) which only works on OSX versions 10.10 (Yosemite) or newer.
+DLite depends on [xhyve](https://github.com/mist64/xhyve) which only works on OSX versions 10.10 (Yosemite) or newer. You also need a fairly recent mac. You can tell if your computer is new enough by running `sysctl kern.hv_support` in a terminal. If you see `kern.hv_support: 1` as a response, you're good to go. If not, unfortunately your computer is too old to leverage the hypervisor framework and DLite won't work for you.
 
 Xhyve, and therefor DLite, does not support sparse disk images. This means that when you create a virtual machine with DLite the *full size* of the image must be allocated up front. There is ongoing work to support sparse images in xhyve, and once that support lands DLite will be able to take advantage of it. See [xhyve#80](https://github.com/mist64/xhyve/pull/80), [xhyve#82](https://github.com/mist64/xhyve/pull/82), and [xhyve-xyz/xhyve#1](https://github.com/xhyve-xyz/xhyve/pull/1) for more information.