What are the Mac Pro models?
The Mac Pro Model 1,1 was released in August of 2006. This 32-bit machine featured the Intel 5000X chipset, as well as two 2.66 GHz dual core Intel Xeon processors. Mac Pro DDR2 RAM 667MHz came with an original configuration of 1GB (2x512MB), and an nVidia GeForce 7300 graphics card with 256 MB or GDDR3 SDRAM. It included a 250 GB Serial ATA hard drive, a 16x SuperDrive optical drive, and uses OS X 10.7 Lion, although one can upgrade to Mountain Lion.
Model ID 2,1 (DDR2 667MHz): Out in April of 2007, this device is very similar to the 1,1. The only real difference here is the optional 3 GHz quad core processor.
Model ID 3,1 (DDR2 800MHz): Released in Jan of 2008, the machine is 32-bit in Mac OS X client and 64-bit in Mac OS X server. They include the Intel 5400 chipset, two 2.8 GHz Intel quad core processors, a 1600 MHz bus, and 2 GB of 800 MHz DDR2 memory. For graphics, it has an ATI Radeon HD 2600 XT with 256 MB of GDDR3 SCRAM. The hard drive is a 320 GB Serial ATA. It features the same type of optical drive as the previous models, and it operates on the Mountain Lion OS.
What about the Newest Models?
The preceding models are those you might still be able to find used today, but chances are you are going to be looking at the different and newer models that are out right now. These include the Mac Pro 4,1, and the different versions of the 5,1.
Model ID 4,1 (DDR2 1066MHz): Released in March of 2009, the Mac Pro 4,1 quad-core features a 2.66 GHz. The Mac Pro 4,1 model could also come with two 2.26 GHz quad core Intel Xeon processors (8-core.) They have a 4.8 GT/s system bus, 3 GB of memory and up to 6 GB of memory. For the graphics, it includes the nVidia GeForce GT 120, which has 512 MB of GDDR3 SDRAM. The hard drive is a 640 GB Serial ATA. This machine has an 18x SuperDrive with double layer support as an optical drive. This machine also uses OX X 10.8 Mountain Lion.
Model ID 5,1 (DDR3 1066Mhz or 1333MHz): With this machine, you will find a number of different options, as they released the first version in August of 2010, and the latest of the 5,1 in June of 2012. Both utilize the Intel x58 chipset. The earlier model had a 2.8 GHz quad core Intel Xeon processor, two 2.4 GHz quad core processors (8-core), or two 2.66 GHz Intel Xeon 6-core processors (12-core.) The 2012 model featured a 3.2 GHz quad core processor, a 3.33 Ghz 6-core, or three different 12-core configurations. The 2010 version had a base configuration of 3 GB of memory for quad- and 6-core models, and 6 GB of ram for the 8- and 12-core models. The 2012 version had a base configuration of 6 GB of memory for the quad and 6-core models, and 12 GB for the 12-core models.
The graphics card in the 2010 model has an nVidia GeForce GT 120 with 512 MB of GDDR3 SDRAM, and the newer version has the ATI Radeon HD 5770 with 1 GB of GDDR5 memory. For hard drives, the 2010 models featured a 640 GB Serial ATA, and the 2012 version has a 1 TB Serial ATA. Both of the versions utilize OS X 10.8 Mountain Lion as the operating system.