XPS M1530 graphics... DDR2 or DDR3?

Can someone tell me whether the XPS M1530 NVIDIA 8600M graphics card uses DDR2 or DDR3 RAM?  I've seen two reviews that say it's DDR3 ( http://www.notebookreview.com/default.asp?newsID=4127 and http://www.notebookcheck.net/Review-Dell-XPS-M1530-Notebook.7295.0.html), while I thought I saw on the Dell website somewhere that it's DDR2.   Which is is?