OverclockingTo find the maximum overclock of our card we used a combination of ATITool's successor (work in progress) and our benchmarking suite.
The final overclocks of our card are 715 MHz core (24 % overclock) and 1254 MHz Memory (26% overclock). Both overclocks are absolutely stunning. It seems that the GTX 260 can easily handle running at GTX 280 clock speeds (602 / 1107). So if you are willing to do some overclocking you can buy one of these cards and overclock them to GTX 280 performance levels. You will miss 48 shaders and 128 MB of memory, but this could be offset by going beyond the GTX 280's default clock. Compared to ATI's latest offerings overclocking is easy and widely supported by overclocking utilities.
Please note that due to the PLL design and clock frequency relationships overclocking the GTX 280 is not completely trivial.
- The core clock can not be higher than shader clock / 2. If the core clock goes beyond that it will be set to 1/10th of what is requested. For example if you set 600 MHz with a shader clock of 1200 MHz it will work. But if you set 601 MHz with 1200 MHz Shader, the actual operating core frequency will be a mere 60 MHz.
- I also noticed that if the shader frequency is too high in relation to the core frequency, the card will instantly render artifacts.
- Last but not least, changing the PCI-Express clock frequency, causes the card to change clocks as outlined in this article.
The temperatures look fine, even with heavy overclocking the card only reaches 90°C.