I've searched the forum and I'm not finding any concrete threads about my question, so if it's already been ask/done, please overlook me and help point me into the right direction. So what I want to do is upgrade my Mac Pro 1,1 which I believe is a 2006 model. I'm wanting to start with my processors. I know what I need to know about the RAM, so that's not an issue. My Mac has 2 - 2.66ghz dual core Xeon's and according to the Apple website they are the 5100 series processors. By using this forum, I believe them to be 5150 Woodcrest Xeon's according to the information found HERE. I'm wanting to upgrade to dual quad core Xeon's. The ones I'm wondering about are Intel L5420 Xeon's which are socket LGA771 Harpertown's. Can anyone tell me if this is possible without changing anything other than dropping them and being done with it. I don't want to mod my Mac or do anything else to it other than upgrading the RAM, it's only got 2gb and I'd like more. If those processors won't work, can anybody tell me which ones will that are quad cores. I'd appreciate any and all help/advice. Thanks!