how can make multiple Geforce GTX 280 works?

I have 3 Geforce GTX 280, and I want to use them in RedHat Linux 5.2. After I installed the Linux, the system is very very slow and can’t be used. What can I do now? thanks!
And what should I do else when coding of CUDA, that can boost my application with the second and the third GPU? Can I get 3 times speed than one card?
Any suggestions are be very appreciated!

Very slow meaning what exactly? Which NVIDIA driver did you install?

The PC runs very slowly for any operation, for example, start-up or only open a terminal needs very much time. But if I use only one graphic card of Geforce GTX 280, it can work normally.

Thank you!

I am plan to build a system similar to yours. Now I am confused by the various graphics card and motherboard. What motherboard and graphics card do you use? thanks

just wildly guessing here. Maybe you do not have enough power to feed all your hardware?

yeah… I have three 280s on a 64-bit linux system whith the newest driver and had no problems, see link.