There is no mistaking the "Late 2013" Mac Pro models for earlier ones as they present an Apple described "radical" departure from the large, highly expandable tower case design of yore and instead feature a compact dark gray, glossy cylinder design that is approximately one eighth of the mass but has limited internal expansion.
Apple explains that these "Space Gray" cylinder Mac Pro models are "designed around an innovative unified thermal core" and have not only faster processors than earlier models but also dual workstation class graphics processors, faster memory, and faster PCIe 2.0 x4 flash storage. Instead of internal expansion, the system provides extensive high speed ports for external connectivity options.
The Mac Pro "Eight Core" 3.0 (Late 2013) originally was a "custom-order" configuration of either the Mac Pro "Quad Core" 3.7 (Late 2013) or Mac Pro "Six Core" 3.5 (Late 2013), but Apple made it a standard configuration at a lower price point on April 4, 2017.
The Mac Pro "Eight Core" 3.0 (Late 2013) features a single 3.0 GHz Eight Core 22-nm Xeon E5-1680v2 processor with a dedicated 256k of L2 cache for each core and 25MB of level 3 "Smart Cache." If otherwise equipped as the default models, the original configurations of this model have either 12 GB or 16GB of 1866 MHz DDR3 ECC SDRAM, a 256 GB SSD, and dual AMD FirePro D300 or D500 graphics processors with 2 GB or 3GB of GDDR5 memory each, respectively. The standard configuration quietly released on April 4, 2017, has 16GB of 1866 MHz DDR3 ECC SDRAM, a 256 GB SSD, and dual AMD FirePro D700 graphics processors with 6GB of GDDR5 memory each.
Connectivity of all Cylinder Mac Pro models includes six Thunderbolt 2 ports, one HDMI 1.4 UltraHD port, 4 USB 3.0 ports, and Dual Gigabit Ethernet ports along with 802.11ac and Bluetooth 4.0.
Originally, this model reportedly supported as many as three 4K displays or six Thunderbolt displays. However, on June 16, 2015, without updating the graphics cards themselves, Apple quietly increased the official support to as many as three 5K displays (5120x2880) -- two using Thunderbolt 2 ports and one using the HDMI port. The support for as many as six 2560x1600 displays using all six Thunderbolt 2 ports remained unchanged.