Operating System :Windows 7 Home & Pro. MAR, Windows 10 Home & Pro MAR, Ubuntu Linux, Free DOS Chipset :Intel C612 chipset Processors :Intel® Xeon processor E5-1600 v3 Series plus select Intel Xeon E5-2600 v3 Memory Support :Quad channel;,Up to 256GB10 2133MHz DDR4 ECC RDIMM memory, 8 DIMM slots Hard Drive :SATA or SSD Removable Media :Optional Expansion Bays :One external slimline optical bay; Two internal 3.5" hard drive bays; one external 5.25" bay Expansion Slots :Two PCIe x16 Gen 3; one PCIe x16 Gen 3 wired x8 (HL); one PCIe x16 Gen 2 wired x4; one PCIe x1 Gen 2; One PCI 32bit Graphics :Support for two PCI Express x16 Gen 2 or Gen 3 graphics cards up to 300W Audio :Integrated: Realtek ALC3220 High Definition Audio Communications :Integrated Intel I217 Gigabit Ethernet controller I/O Ports :Front: Three USB 2.0, One USB 3.0, Mic/Headphone; Rear: Three USB 2.0, Three USB 3.0, Two PS2, One Serial Power :80 Plus? Gold Certified, 90% efficient): 685W or 425W Dimensions :(HxWxD): 16.30 x 6.79 x 18.54"; 414 x 172.6 x 471mm Weight :N/A