Originally Posted by Arensethar
Wait, so they honestly went with a 192-bit bus on one of their higher-end cards? That's strange... almost always it's been 256-bit or larger. And memory bus size can have a fairly damn big effect. Going from my GTS 450 with a 128-bit bus to my 560ti with a 256-bit one, made a massive difference, and the 128-bit bus was clearly a limiting factor for bandwidth hugely at times back when i was still using it. It gets to a point where no matter what speed the memory is running at, the bus width will simply cripple its performance. I even tried overclocking my memory speed on my gts 450 a fair bit and it didn't make that big of a performance boost at all.
they went with 192bit simply because it's the same GPU as the 670-680 (GK104), and they needed to make it slower somehow to justify the prices, cutting back 64bit from the memory bus was a way of doing it, but you need to remember that memory clock is really high, so it can beat a 384bit GTX 580 without much trouble...
as for the GTS 450, it's hardly only the memory bus that is limiting it... 192 "cuda cores", 32TMUs... your 560 Ti have 384 "cuda cores" and 64TMUs, 32 ROPs vs 16ROPs.
(and actually the GTS 450 chip had support for 192bit memory, but NV decided to sell it with 128bit only active, later they released the 550 Ti, based on the same design but utilizing the entire chip, and the 192bit bus)
7770 is much faster than the GTS 450 and it's also a 128bit card.... and you could make a 128bit card even faster,