Hashrate on old cards vs. new cards

Hi there. I've been mining on 470/480, I have an assortment of models, with 4gb and 8gb and started a new rig now with 6 280x I found a good deal on, second hand. I realize that these older cards, about 3 generations back, mine at the same hashrate as my 470/480, give or take at 280-300 H/s. As for power consumption, with a little undervolting on the 280x, I get very close to the 470/480 catds, at about 160-180w per card. Now with the new 570/580 cards, for which I see reports that the hashrate is still the same, it appears as if there has been virtually no change in hashing power in years. What's up with that? Has the technology stayed the same? Maybe that means that mining software may still improve as far as the newer generations? Your thoughts would be appreciated...

@DrYM With the newer generation cards, they use a different semiconductor fabrication process (14 nm for the 480/470 vs. 28 nm for the 280), which mainly results in lower manufacturing costs (i.e. higher profit for AMD). In addition, the new cards generally have higher clock speeds and a lot more VRAM, and these are the kind of improvements that result in better gaming/rendering performance, which is really what GPUs are made for.

The main reason these improvements don't translate into better hashing performance has to do with the Equihash algorithm, since it's dependent on memory. It's not the total amount of memory available that's the limiting factor, but rather the memory bandwidth, which depends on both the size of memory bus width and memory clock. Here's a comparison of some of the most commonly used GPUs and their respective memory bandwidth:

280 - 288 GB/s
290 - 320 GB/s
380 - 256 GB/s
390 - 384 GB/s
Fury X - 512 GB/s
480 - 256 GB/s

As you can see, these numbers loosely correlate to each card's Equihash performance (480 < 290 < 390 < Fury X).

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