A while back I received a Mac Pro 2,1 that had been junked. I would like to share what I learned about it. Apple sold the 2,1 as an 8 core upgrade of the 1,1. They didn’t say anything else was changed if you look at the available info. This was rather misleading, a LOT was changed. Many people seem to think the 2,1 is really just a 1,1 with different cpu’s, this is completely wrong. Going over the 2,1 has been very interesting. I have a lot of experience with Mac Pro’s, but this was my first 2,1. Almost nothing in it is directly from a 1,1. The entire case, front fan unit (with 2 screws), magnetic cpu cover, and power supply, are like a 3,1. The memory box, is a hybrid of 1,1 and 3,1. It fits the 1,1 risers, but has the magnetic cpu cover section like a 3,1. The heatsinks are unique, being similar to a 3,1 with 3 full length heat pipes each, and plastic support blocks in the base, but they are different in that the base is cut differently than a 1,1 or 3,1. The motherboard, is unique, it is NOT a 1,1 or 3,1 type. its similar to a 1,1 but some items have been moved around near the cpu’s. It has both heatsink sensor plugs on the left side of the cpu sockets, and includes the 3,1 style cpu mount block bosses. It also uses a 1,1 style northbridge heatsink. In trying to repair this 2,1 I first replaced the motherboard. I don’t have another 2,1 board, so used a 1,1 board and flashed it to 2,1. It is a drop in replacement as long as you remove the cpu heatsink support blocks, and reroute the lower cpu sensor cable to the right side. I ran into a problem with removing the cpu’s, they were glued to the heatsinks. The silver metal heat paste that apple used is like epoxy or something, and it took so much force to pry the heatsink off the cpus that I broke one cpu socket, and bent the metal retaining brace on the other. The cpu’s luckily were not damaged, and I swapped them to the flashed 1,1 board. The special 2,1 heatsinks are usable on the 1,1 board once the temp sensor wire is rerouted in the lower heatsink, the wire is long enough to allow this. The plastic support blocks cannot be used since the 1,1 board has chips where they would be placed. The system then started up and seemed to work, but the ram was getting very hot. I tried some things, and due to high temps on the ram I stopped using the computer. My guess is the PSU is somehow bad and putting out bad voltages. I don’t want to risk any more of my fbdimms to experiment with it. Changing ram risers didn’t fix it either. I learned about the 3,1 power supply when planning to swap a PSU from a spare 1,1 I have. The 2,1 has the metal cover behind the dvd bay that hides the power cables, and the PSU is 3,1 type. I don’t have a 3,1 to take parts from, so the 2,1 is out of commission for the time being. I either need another 2,1 or 3,1 to take parts from. Anyway, just wanted to share, hope this info is useful to somebody when fixing their 2,1.