PROGRAMMERS CAN WORK MIRACLES--
But all I have heard for a year is that there is not much juice to squeeze from the DAG. Generating it on-the-fly was a big thing, saving start-up minutes.
Likely, card optimization will be the way to go. 29MH/s on the RX 480 is top speed reported. Newcards (480x, 490, etc) are still top secret, not expected until next year. I search, and se the same old tech blogs. --scryptr
Unless you can find a flaw in the ethash algorithm, it is impossible to get more than 32Mh/s from a card like the RX480 with 256GB/s of memory bandwidth (i.e. memory clocked at 2Ghz). This is because each hash requires 8MB of random memory reads.
THANK YOU FOR THE EXPLANATION--
I think that you have explained the theoretical maximum hashrate for an RX 480. Looking at posted data from various sources, a well tuned RX 480 Ethereum rig will mine at 29MH/s, and an RX 470 rig will mine at 27MH/s per card. It may take BIOS mods and a carefully adjusted OS to get there. Out of the box, the cards will mine at 22-24MH/s completely stock. RX 460 cards will reportedly mine at 10-11MH/s stock, similar to the performance of a previous generation R7 370 card, but at as little as 1/2 the wattage.
I have seen posts at higher hash rates for single-card rigs running a short duration, but none more than the theoretical maximum as you explained it.
The next generation of cards (Vega) may be a game changer, or may not. The top cards will be using a new memory type, and that does not always translate to better mining performance. I keep looking for new information, but it has not surfaced yet. --scryptr