Although this model was offered as a custom configuration of the Mac Pro "Quad Core" 3.2 Server (2012/Nehalem), it has significant technical differences.
The Mac Pro "Twelve Core" 2.66 Server (Mid-2012/Westmere) features two 2.66 GHz Six Core 32-nm Xeon X5650 (Westmere) processors with a dedicated 256k of L2 cache for each core and 12MB of "fully shared" L3 cache per processor.
By default, it is configured with 8GB of 1333 MHz DDR3 ECC SDRAM, two 1TB (7200 RPM, 32 MB cache) 3Gb/s Serial ATA hard drives, an 18X dual-layer "SuperDrive" and an ATI Radeon HD 5770 graphics card with 1GB of GDDR5 memory.
Expansion includes two external 5.25" "optical" bays (one available by default), four internal 3.5" "cable-free, direct attach" hard drive bays (three available by default), and four PCIe 2.0 slots (one free PCIe 2.0 x16 slot and two free PCIe 2.0 x4 slots with the default single graphics card installed).
Port selection includes five USB 2.0 ports, four Firewire "800" ports, dual Gigabit Ethernet, two Mini DisplayPorts and a dual-link DVI port, and more. AirPort Extreme (802.11a/b/g/n) and Bluetooth 2.1+EDR comes standard.
Please note that the "Mid-2012" Mac Pro Server models practically are identical to the "Mid-2010" Server models before them, but there are some differences in terms of specs and identifiers and EveryMac.com has documented them as distinct models, accordingly.