Soleron on 16 January 2009
No, you can't.
SLI only runs on Nvidia boards and certain X58 boards with the Nvidia bridge chip. The P45 does not support SLI. However it will support single-card SLI like the 9800GX2 or GTX295.
It does support Crossfire though, so if you want a multi-GPU setup then go for Radeon cards. Incidentally, the HD4850 will outperorm the 9800GTX by a large margin at a lower price.
