Tryid it on 280x
Got 12-13mh per one(8.1x64, cm9.
...nothing change from 15.12 driver. Stupid amd didn't applied their fix to truly good cards 
Got 12-13mh per one(8.1x64, cm9.
...nothing change from 15.12 driver. Stupid amd didn't applied their fix to truly good cards It didn't change because the R9 280x didn't suffer from the issue that the driver was intended to fix.
The 280x was never a "truely good" ETH card in the first place - that was the 290 and to a lesser degree the 290x.
Tahiti is arguably the best performance/price ratio for FP64 anyone ever released, but ETH doesn't use floating point....
The 7970/280x was actually very good at ETH only at the beginning. With DaggerCoins at Epoch #0 or #1 or so it can get like 28MH/s. And a year ago you could of found them on Craigslist for $100 second hand. The R9 290 while it was a little faster was always expensive to buy because it had high demand for gamers and was hard to find for less than $200. So the 280x was a better choice if it wasn't for the DAG bug.