ChaoSXDemon

Jun 11 2009, 08:10 PM

mcguire720

Jun 11 2009, 05:45 PM

Mines in my signature, but i've been thinking about upgrading to a GTX275 possibly, or perhaps just adding a gts250 in sli.
The biggest thing holding me back now is that i would need a new psu for either option probably

You should NEVER get SLI (Scalable Linker Interface) or CrossFire. They are ABSOLUTELY waste of money and inefficient. There is ALWAYS a single GPU that out runs 2X GPU with less than 2X the single GPU's price. Of course if you are just plane rich then do what ever you want.

*note, NVIDIA calls multi-GPU SLI while ATI calls it CrossFire. They are the identical concept except maybe in technical implementation.

Specifically, 2 times the hardware is NOT 2 times the performance. You see, everything and literally everything has a catch; this is especially so in computer science - all about making choices about which catch to take. In using two GPU (Graphics Processing Unit), a new difficulty is introduced: Synchronization. It is only intuition that this problem arise: given only one monitor with two GPU, how do we divide the screen? Well, here are some of the ways we are using today:

Split Frame Rendering (SFR): Literally the screen's graphical contents are divided into 50/50. The division maybe vertical or horizontal depends on the implementation. Obviously this introduces synchronization problems as if the first half out renders the 2nd half, you will see "broken" images. Therefore, tremendous efforts have been put into dealing with this issue and hence lowering the performance.

Alternate Frame Rendering (AFR): Each graphics card would render a completely scene by it self. However, as one renders say 1st scene, the other graphics card renders the 2nd scene. Needless to say, synchronization is again a concern.

There are other minor effects that SLI/CrossFire supports. But basically they just split the jobs between the two cards which also has to deal with synchronization problems.

In conclusion, at least for now, there are always better single GPU than multiple combined ones. GPUs unlike CPUs, do not really have the concepts of thread. I mean CPU can operate over many software like say you are listening to music while browsing internet and at the same time downloading movie and maybe updating system. Multi-CPU allows true separate threading which allows true simultaneous execution of different software. Graphics....not so much as there is only 1 Graphics API (usually OpenGL, or DirectX).

Hopefully you have learned something and have convinced to only get a powerful single GPU instead of 2XGPU.