I've got an xseries 350 (8682-5RY) with two cpus and want to add two more to max it out. The cpus in the machine are 700/100/2M SL49S. I found a good deal on a pair of SL49R cpus that are also 700/100/2M so I bought them. However, I can't get them to work in the machine, getting a CPU error...