We just got a look at Apple's new Mac Pro, and it is very, very small. Much smaller than you'd think — though pulling the cover off reveals that it's absolutely packed inside. It's one of the tightest packages we've ever seen. All of the I/O is on the back panel, which is accessible through a cutout in the cover; you have to disconnect everything to pull the cover off. When asked about expansion, Apple reps told the crowd that Thunderbolt 2 would be ideal for connecting PCI expansion chassis, but didn't offer too much additional detail.
One thing we couldn't see was the fan. Those dual AMD GPUs and that Xeon processor aren't going to run super cool under heavy workloads, and it looks like all that heat is going to go out the bottom of the casing. We're digging for more info right now. Let us know what you're curious about.
Update: We've figured out where the fan is located — it's at the top of the Mac Pro, and it pulls air up through the bottom of the computer and out the top.