It's not, some of the people who have unlocked have tested with the R 290 bios at the exact same clocks as what they get with the R 290x.
there's still an increase in performance at the same clock speeds, so it's unlocking.
Others stripped the coolers off their cards and compared part...
There's one on rage3d IMO, named himself after an AMD cpu, has a total of like 45 posts, all of them bad mouthing AMD products, and how Nvidia's everything is better.
Nope nothing gets unlocked, but you can flash a 290 X bios to them, the guys on OCUK did so, it let them up the voltages more when they used an Asus? 290 x bios.
Thing is here up in canada land prices have started to go UP again on the 780's
They dropped to a low of about $520 the day they said the price drops would happen, then started to climb north again to $550-560+ and that's for reference stock cooler ones as well.
Unless your wanting to future proof for 1080p with everything maxed out and using a 120hz/144hz monitor and want to use vsync. then I suppose it's worth it.
http://forums.overclockers.co.uk/showthread.php?t=18551534
They show the R 290 results as well "Blurred" out but we know what they are, they even left the OC result listed
R290 OC - 1115MHz / 5700MHz
but then they noticed the slip up a few mins after the post went up and edited it to -...