Overclocking the Nvidia GeForce GTS 450

In our recent overclocking tests of the Nvidia GeForce GTX 460 and GTX 465, we found that pushing the cards to their performance limits essentially provided the equivalent of a free upgrade. After all, the overclocked GTX 460 outperformed a stock-clocked GTX 465, and upping the GTX 465's clock speed boosted performance up to 20 percent. So when Nvidia touted its bargain-priced GeForce GTS 450 video card ($129 list) as being highly overclockable, we were anxious to put it to the test and see if it too might reach into the performance range of its more expensive big brother.
Video card performance is about a lot more than just clock speed. Though the GTS 450 is a decent performer at resolutions of 1,680 by 1,050 or lower, its hardware is pretty stripped down compared to the GTX 460 and higher cards.

Spec	GTS 450	GTX 460	GTX 465
CUDA Cores	192	336	352
Streaming Multiprocessors (SMs)	4	7	11
Memory Bandwidth	128 bits	192 bits (768MB version)	256 bits
Stock Core Clock Speed	783 MHz	675 MHz	607 MHz

As you can see, the lower-end cards actually have faster clock speeds. But with fewer CUDA cores and SMs, and a narrower memory bandwidth, each of the individual components in the GPU has to do more work to render an image, so higher clock speeds become necessary just to maintain a baseline of performance.
In this story, we take the stock GeForce GTS 450 card and, using the standard software available from the card's designer and some trial and error, determine just how fast it can run without introducing instability to the system. What we find is that, once you cut back the number of cylinders under the hood far enough, running them at a higher RPM seems to have diminishing returns.
Though we did get a noticeable speedup from the GTS 450 when we pushed its clock rates higher, the results didn't edge it into the performance territory of pricier cards. Let's take a closer look.
Source:http://www.extremetech.com/article2/0,2845,2369472,00.asp