Kowai said:
The GTX 970 physically has 4GB card and no, the 3.5GB also runs slower than what it was advertised.
3.5GB only runs at 192GB/S, it was advertised that memory will run at 224GB/S. 0.5GB runs at 24GB/s.
The 970 has about a 40% higher clock speed than the 290. And it also has about x2 lower TDP, also it runs significantly cooler compared to the 290x.
I know it's 4GB but it all runs slower than advertised and 0.5GB of it runs even slower than the rest.
The fact is it really isn't that big of a deal as far as performance goes, the biggest issue comes down to the false advertising, if they would have advertised the 970 as having 3.5Gb nobody would say it's a bad card.
But there's an actual BANDWIDTH issue. Not just memory issue. Ultimately due to the design of the crossbars and the memory controllers, it is not possible for 1 crossbar port to carry the full load of 2 memory channels in all circumstances. The crossbar port and its attached ROP/L2 unit can access both memory channels at once, splitting up the 4 operations among them, but there is only 1 read return bus and 1 write data bas, and hence in practice it cannot issue identical operations to both memory channels at once . As a result NVIDIA has segmented the GTX 970’s memory into the now-familiar 3.5GB and 512MB segments. In the case of the 3.5GB segment, this behaves otherwise identically to a fully enabled card such as the GTX 980, with the 1KB stride being striped over 7 crossbar ports, and hence 7 DRAM modules. Meanwhile the 8th and final DRAM module sits in its own 512MB segment, and must be addressed by the crossbar on its own.
This in turn is why the 224GB/sec memory bandwidth number for the GTX 970 is technically correct and yet still not entirely useful as we move past the memory controllers, as it is not possible to actually get that much bandwidth at once when doing a pure read or a pure write. In the case of pure reads for example, GTX 970 can read the 3.5GB segment at 196GB/sec (7GHz * 7 ports * 32-bits), or it can read the 512MB segment at 28GB/sec, but it cannot read from both at once; it is a true XOR situation. The same is also true for writes, as only one segment can be written to at a time." (quoting Aesthetics from HF as he's very knowledgeable)
and seeing as nearly all AAA games uses above 3.5GB and future proofing is not existent on this card. Sure its not problem when you crank AA all way down to bare minimum, but who buys $400 card to do bare minimum, especially when cards can do more than just that for the same price.
Therefore, the 290x outperforms it when it comes to resolution and AA.
Most aftermarket 290x's will perform under 80 degrees celcius and not too loud