Most modern graphics cards for desktop client PCs have four display outputs and can drive up to four monitors. By contrast, some professional boards have six outputs and can work with six displays at once. Intel's upcoming Arc Alchemist discrete GPUs will support a rather mysterious fifth display output.
"DG2 supports a 5th display output, which the hardware refers to as 'TC1,' even though it isn't a Type-C output," wrote Matt Roper, an Intel engineer, in a note for a Linux driver patch (discovered by Phoronix). "This behaves similarly to the TC1 on past platforms with just a couple of minor differences."
Supporting five display outputs on a graphics card is a bit odd, since many of those who use multi-display configurations consisting of over three monitors tend to use an even number of monitors. This is why AMD's Radeon Pro W6800 is equipped with six mDP 1.4 outputs, whereas various professional boards from Nvidia and Matrox graphics have four or even eight outputs.
All of the DG2 prototypes that have been pictured so far had four outputs, so perhaps the fifth is reserved for professional or special-purpose boards. Meanwhile, one has to remember that DG2 supports DisplayPort 2.0 with UHBR 20 with its whopping 77.37 Gbps bandwidth and a new set of features. Perhaps — we are speculating now — Intel simply could not fit more DP 2.0 transmitters into its design and decided to stick to a rather strange number of display pipelines. Alternatively (again, speculating), since one DP 2.0 active/tethered cable can deliver enough bandwidth to drive more than one display, one may not need more than five outputs and pipelines to enable multi-monitor configurations for applications like videowalls.
For those not familiar with display pipelines and display outputs/interfaces: pipelines are GPU hardware resources that are necessary to send a picture to an output device, whereas outputs are physical interfaces. DG2 appears to have four 'regular' display pipelines/ports marked DDI-A, DDI-B, DDI-C, and DDI-D as well as one TC1-type port marked as DDI-J.
Regular ports are used for standard display interfaces, including DisplayPort, embedded DisplayPort (eDP), HDMI, and LVDS. By contrast, TC ports can be used to route DP display signals to Thunderbolt 3/4 or USB 3.2/USB 4 outputs using dp_alt_mode/tc_port_tbt_alt mode. Meanwhile, the total number of display outputs/interfaces typically does not exceed the GPU's total number of display pipelines. Based on the fact that Intel's DG2 drivers currently list five different DDI ports, it looks like the standalone GPUs could indeed have five display pipelines.
All modern Intel integrated GPUs have four display pipelines and can drive up to four displays when equipped with appropriate physical interfaces. When it comes to laptops, Intel's processors support an internal display and up to three additional monitors, though many things depend on the exact implementation. For quite a while, Intel used TC1 (Type-C) ports on its desktop CPUs to enable conventional display interfaces (e.g., Rocket Lake has two TC ports, but does not connect to Type-C outputs by default). So it's perhaps not surprising that DG2 may use the same solution to enable its fifth display output.
