Next to the power supplies flat onto the motherboard on the back edge.  There should be a plastic cover/plug/placeholder on the chassis where the RJ45 port goes - it needs to be removed.  You will probably also need to remove the rear fans to fully access the DRAC slot.  RAC_CONN: <ADMIN NOTE: Broken link has been removed from this post by Dell> Installation Instructions:[URL]      
Hello, I ordered a DRAC 4i card for my PE 2850 on eBay and finally received it in the mail this week. I was curious as to where it actually gets installed on the motherboard as I can't find the proper connection, or how the RJ45 connection would seat in the back of the machine.  I assume the 4i cards install on the PE2850? I couldn't find a hardware installation reference anywhere on google so thought I'd post here. Cheers' GnarlyN
Installing DRAC4i on PE2850