each), and PCIe-based flash storage. There is a 3× MIMO antenna system for the unit's 802.11ac WiFi networking interface, Bluetooth 4.0 to facilitate close-range wireless functions such as music transfer, keyboards, mice, tablets, speakers, security, cameras, and printers. The system can simultaneously support six Apple Thunderbolt Displays, or three 4K resolution computer monitors. The cylindrical Mac Pro has a redesigned configuration of ports. It has a HDMI 1.4 port, dual Gigabit Ethernet ports, six Thunderbolt 2 ports, four USB 3 ports, and combined digital Mini-TOSlink optical / analog 3.5 mm stereo mini jack for audio output. It also has a headphones mini jack (the two are distinctly selectable within the Sound System Preference panel, Output tab). There is no dedicated port for inputting audio. The system has a low-fidelity internal mono speaker. The Thunderbolt 2 ports support up to thirty-six Thunderbolt devices (six per port) and can concurrently support up to three 4K displays. This design requires two GPUs to support the seven display outputs (HDMI and six Thunderbolt). The I/O panel illuminates itself when the unit senses it has been moved to make it easier for the user to see the ports. Unlike the previous model, it has no FireWire 800 ports, dedicated digital audio in/out ports, a SuperDrive, DVI port, 3.5-inch drive bays for replaceable storage drives, or changeable internal PCIe slots. Instead, there are six Thunderbolt 2 ports to connect high-speed external peripherals, including enclosures for internal PCIe cards. Apple's website mentions only RAM and flash storage as user-serviceable, though third party tear-downs show nearly all components can be removed and replaced. However, special tools only available from Apple are necessary for proper dismantling and reassembly. Apple has also specified mandatory and recommended tightening torque values for nearly every screw, with the most important being those securing the GPUs and CPU riser card to the thermal core. According to Apple, not tightening screws to the mandatory torque values may result in damage or malfunction. A lock switch on the aluminum housing allows for easy access to the internals, as well as fitting a security lock with its own cable, and components are secured with Torx screws. The flash storage and GPUs use proprietary connectors and are specially sized to fit into the enclosure. The CPU is not soldered to the riser card and can be replaced with another LGA 2011 socket processor, including processor options not offered