There's a review of both cards in the latest c't Magazine [1] (German) - the benchmarks suggest that the AMD card wins in most disciplines, except for tesselation benchmarks and a couple of games at lower resolutions. AMD's OpenGL drivers are also (and have always been) much worse than nvidia's in various respects, so the nvidia card wins on more OpenGL-based benchmarks.
Both cards seem completely removed from reality though, as they apparently sound like jet engines under load, consume almost 400 Watts of power, and the 590GTX actually throttles itself if you run it under certain loads (such as Furmark) to avoid overheating/drawing too much current. Oh, and they cost over €600. I realise "maker of the fastest graphics card" is a marketing thing, but it's pretty meaningless in practice.
FWIW, if you want to spend a lot of money on graphics cards, you're probably better off buying a fairly high-end model (but not top-of-the-range) every hardware iteration, usually 6-12 months, and selling the previous one instead of dropping a crapload of money in one go.
How do bitcoins compare to the cost of electricity? I've got a (fairly modest) Radeon HD 5770, which consumes around 100W under load. At €0.20/kWh, that's €0.48/day (leaving aside the power needed for running the rest of the system). For sake of argument, let's say I can get 2BTC/day with this hardware. Is that worth more than the 48 cents it cost me to do the calculations? (sorry if the answer to this is obvious, I've only heard of bitcoins, never looked into them)
This aside from the moral concern about the environmental impact of wasting energy on pointless hash calculations. I probably waste more energy in other, albeit less obvious ways.
I would be worried about how thin the market is though, as each significant price increase seems to relate to a specific piece in the online tech press. In that way it has a lot in common technically with a pump and dump scheme. As long as you're running a small enough farm I suppose I wouldn't worry too much about it as long as you're philosophically good with the increased energy use.
If it's a waste, than banks computer farms is a waste too.
Sorry, I don't understand this part. I'm pretty sure real currency isn't backed by hash function brute forcing. (I assume they use contracts along with some form of public key cryptographic hashing to sign transactions.)
> the benchmarks suggest that the AMD card wins in most disciplines
Anandtech's 590 review [0] does not really agree. It sees the cards as a wash overall (though the choice of games benched will influence the winner a lot), compute is NVidia's domain, and the 590 is significantly quieter than the jet turbine of the 6990 (60dB versus an incredible 70dB on HAWX)
Both cards seem completely removed from reality though, as they apparently sound like jet engines under load, consume almost 400 Watts of power, and the 590GTX actually throttles itself if you run it under certain loads (such as Furmark) to avoid overheating/drawing too much current. Oh, and they cost over €600. I realise "maker of the fastest graphics card" is a marketing thing, but it's pretty meaningless in practice.
FWIW, if you want to spend a lot of money on graphics cards, you're probably better off buying a fairly high-end model (but not top-of-the-range) every hardware iteration, usually 6-12 months, and selling the previous one instead of dropping a crapload of money in one go.
[1] 590GTX review: http://www.heise.de/ct/artikel/Gegenangriff-1213480.html
6990HD review: http://www.heise.de/ct/inhalt/2011/08/74/