The MacPro Xeon tower machines are incredibly fast workstations. You can make yours even faster by adding a Solid State Drive (SSD) as a boot drive and/or as a scratch file drive. An SSD equipped machine boots very quickly and loads applications faster than a hard drive. A SSD used as a swap or scratch disk for Photoshop, Final Cut, and other media production software can improve the speed of the program when you are doing intense work.
One issue is that the MacPro drive bays are not compatible with the 2.5″ format of SSD drives, and conventional 2.5″ to 3.5″ mounting brackets do not work.
The solution is the IcyDock MB882SP-1S-2B , a caddy for the SSD drive which has SATA connections in exactly the right place to mate with the MacPro backplane. Install the SSD into the IcyDock, and then slide the IcyDock into the Mac just like a full sized drive.
CanadaRAM.com stocks the IcyDock and a wide range of SSD drives.