6xxx does support it, it's just slower than 7xxx. I don't bother because I don't want the perf hit (even with these improvements) as I care more about high refresh rate/resolution support but good to see nevertheless, particularly for future cards where performance will improve further.

You might want to upgrade Mesa too as I believe at least some of the RT options should now be enabled by default, but I haven't tested myself. And you can force it with env variables, as the other commenter suggested.