I don't get why people are buying DirectX 10 cards for gaming. Thirty FPS (frames per second) is the verge of when human eyes detect lag (glitchy movement in-game). Anything under 30 will make you sick from looking at it, and anything over 30 you can't really tell the difference. DirectX 10 cards get a max of 30 FPS in DirectX 10 mode. New DirectX 9 cards can get 100+ FPS. So, would I rather buy a DirectX 9 card and get a better frame rate and save money or buy a DirectX 10 card? Both support HDCP. Plus, when you playing First Person Shooter games, you don't have time to look at how realistic the grass looks; you're focused on where the enemy is and where to aim your weapon.

The same thing goes for SLI. If you have two video cards, you have twice the GPU speed, twice the pixel pipe lines, twice the RAM so you should get twice the frame rates, but you don't. You get 10 to 15 more frames per second and every time a new game comes out, Nvidia has to rewrite the drivers to support the new game so is it really worth the $200 - $500 for a second one? I don't think so. If I had an older SLI card, I would sell it and buy a new video card. That would surely give me more than a 10 to 15 frames per second boost.

DirectX 10 is harder to program with, so most applications don't fully optimize it yet. And where do you base DirectX 9 outperforming DirectX 10 cards on FPS on?

Anyways, I personally wouldn't get a DX10 card yet, unless it's really cheap. Because no software vendor is stupid enough to make a solely DX10 game yet.

And rendering is not everything that happens every frame. Usually, a scene is composited and matrices are applied. SLI should in theory double your rendering speed, but it's kind of like dual core, you'll get a speed increase of 40-60%, opposed to a single card.

direct x 10.1 is comming out soon in 2008 and so is geforce 9XYZ. well maybe some people dont nececary need the FPS gaming but more for video processing and stuff like designing graphics. or watching movies BLU RAY etc etc. or maybe u get parts for a cheap prices or free! is halo 3 using Direct X 10?

Graphics designing isn't done on Nvidia in the first place, because they're really instable cards. Especially the 8800 GTS has a lot of problems with the GPU having rendering bugs. ATIs are a lot more stable, and especially the new HD 2900 XT with it's 1024MB of VRAM, and a nice price of €390 is a great card for professional use.

Remember--current "mid-range" (more like budget-special... GeForce 8600GT, Radeon HD 2600XT) DX10 cards are basically performing about 5% better then DX9 mid-range cards (GeForce 7600GT, Radeon x1600/x1650XT). Still, what you're paying for is the fact that they'll run DX10 games. To tell the truth--we don't even have real DX10 benchmarks! Most of the "DX10" benchmarks that are constantly run on the Radeon HD 2000 and GeForce 8000 generations of chips are actually quite fake and a bad performance indicator. Why? Because... it's DX9c with 2 or 3 more "eye candy" items added in, sans optimizations! In real DX10-primary games, they should have code optimized properly that everything that runs at DX10 should be at least two thirds as many FSP as in DX9.

Anyways-the actual "smooth" viewing for gaming is 60fps--no more, no less. Still, quite a few professional gamers will run at medium-low resolutions and highest possible refresh rates (so, for example, using a 21" CRT at 1280x1024)--they argue that highest resolution slows your card down too much--every frame above 60 can be the frame that matters--you don't see them all, but there's a chance you'll see the first indicator of an opponent coming around the corner, being able to react that split second earlier and gain a competitive advantage.

EDIT: Remember that SLI and CrossFire are both limited by interface. They can't communicate with each other as quickly as they can communicate with the processor. Also, though you have double the hardware, you can't double everything. The idea of SLI and CrossFire was to split the load, so you could gain higher image quality and better performance at higher resolutions (remember that the best monitors can display up to 2048x1536 for standard-aspect and 1920x1200 for wide-aspect). Anyways--one thing you can't double for sure is the amount of graphics memory. Each card has its own memory--the greater card would be limited by the lesser card. If one card had 512MB of VRAM and the second card had only 256MB of VRAM, then both cards are limited to 256MB of VRAM. That being said, they both store the same information on each set of RAM--they load the same exact everything as both cards require everything--they don't "share" the information on VRAM with each other.