You'd need to run them at 1:2 ratio, and also have your board around 450FSB. That should run the individual memory chips at 900Mhz real clock rate, which is 1800mhz effective clock rate.
The reality is, you're going to get next to zero benefit from running them that fast. I have yet to fully understand why any manufacturer builds memory over about DDR2/1200, other than the most obvious answer of wanting to make more money.
Hop into the memory forum and look for the "Should I buy DDR2/1200" thread for a writeup as to why it makes essentially zero difference to run your memory faster than FSB. The cliff notes are this: The speed of your memory is the speed between the northbridge and the ram sticks, NOT your CPU and the ram sticks. Thus, if your FSB (the link between the CPU and the northbridge) is slower than the memory speed, the FSB becomes the bottleneck.
It would be like running an AGP 8x card in an old-school PCI slot (ignoring the electrical issues). The bottleneck isn't the card, or the CPU, it's the connection between the two.