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.
Specifically, this model -- the Mac Pro "Six Core" 3.5 (Late 2013) --
is powered by a single 3.5 GHz Six Core 22-nm Xeon E5-1650v2 processor
with a dedicated 256k of level 2 cache for each core
and 12 MB of level 3 "Smart Cache."
This model is configured with 64 GB of 1866 MHz DDR3 ECC SDRAM, a 1 TB SSD, and dual AMD FirePro D500 graphics processors with 3 GB of GDDR5 memory each.
six Thunderbolt 2 ports,
one HDMI 1.4 UltraHD port,
4 USB 3.0 ports,
and Dual Gigabit Ethernet ports
in addition to 802.11ac
and Bluetooth 4.0.
MaxOS has been upgraded to MacOS 11 Big Sur
Please note that stock images are used. Units might show light signs of previous use (scratches etc). Units are fully tested and 100% functional.