Originally Posted by brettjv
None of any of that spec stuff matters for playback of blu-rays and videos from off your hard drive. You can get like a $40-50 GPU (like a gt520) and meet his needs.
All those specs you're asking about ... all they matter for is gaming or other 3D applications.
'Effective' memory clock refers to the fact that this measurement is 4 x the 'actual' memory clock, because DDR5 is what's referred to as 'quad-pumped' ... for every clock cycle, 4 pieces of data can be transferred. So, a 1000MHz 'actual' memory clock has an 'effective' memory clock of 4000MHz with DDR5. With DDR2 and 3, they are only 'double-pumped', meaning that 1000MHz actual = 2000MHz 'Effective'.
However, the memory clock must also be multiplied by the bus width (i.e. 128-bit, 256-bit, etc) in order to calculate memory BANDWIDTH, which is actually the 'important' number in terms of the calculation of how fast the memory is going to work. Roughly speaking, if you had 2000MHz effective memory clock on a 256-bit bus, it'd would have the same bandwidth as 4000MHz effective on a 128-bit bus ... and hence the memory subsystem would perform the same (more or less).
When you get into memory AMOUNTS, it gets tricky. More is not always better (although if it's totally free it's almost always better). Memory is the kind of thing where you either have ENOUGH for what you're trying to do, in which case having extra does NOTHING, or you don't have enough, in which case having more (such that you DO have enough) becomes critical ... i.e. your performance drops way off if you have too little memory. There's a TON of stuff that comes into play with regards to calculating 'how much you need' when it comes to vram, because every game is different. However all these cards have adequate memory for gaming at 1080p resolution or below.
The 2GB card is a joke, because it doesn't have nearly enough GPU power to 'push' an image that actually occupied 2GB worth of memory. Cross that one off your list for sure.
The reason the 460 is better than the 550 is this: the first digit refers to the 'generation' of card, i.e. the 4-series is older than the 5-series. The 2nd (and third in some cases) number though describes the 'level' of the card relative to it's generation. So while the 460 is older, it's a higher level card (6 level vs 5 level) ... usually it takes at least 2 generations before a 5-level card will be better than a 6-level card. So ... the 650 (which hasn't come out yet) may well be better than a 460, but the 550 is not.
LIke I said before though none of these specs apply to 2d movie viewing to any significant extent. These are specs that matter for 3d only. Any remotely decent GPU from 400-series up will rock blu-rays without breaking a sweat.
The best cards on your list for gaming, however, are:
560, 6850, and 460. The other (450 and 550, since they're 5-level cards) are way slower than those three. The regular 560, despite being newer than the 460, is really not much faster at all, because it's really the same technology in the 4 and 5-series afa those particular cards go. The 560 does run cooler though, it's more efficient. To get an actual BETTER 5-series card than the 460 1GB, you have to go with a 560ti 1GB.
Lastly, the core count is by far the most important spec among your cards here. However keep in mind that AMD core count (aka Stream Processors) and nV core count (i.e. CUDA cores) cannot be directly compared using raw counts. The 6850 has far more 'cores' than the nV cards, but it's really about the same speed as the 560 and 460. AMD and nV cores have different architectures.
Does that answer all your questions?