Surrounding the AM4 socket, there are 12 power phases to help deliver stable power, as well as helping to keep the components cool. There is a pair of 4pin fan headers to the right of the top headsink, one of which outputs 1.5A for use with waterpumps. However there doesn't appear to be any RGB headers nearby for the AMD RGB Wraith coolers.
Alongside the 24pin ATX socket, there are two USB 3.1 Gen 1 headers, followed by the RGB and USB headers for the LED Wraith coolers, again to the left there is another 4pin fan header.
Storage wise, there are 6x right angle SATA 6Gb/s ports, however they are set back from the edge of the motherboard, making it difficult to insert a right angle SATA cable, should you with to try this orientation.
In the bottom left corner of the motherboard we find the standard array of front panel headers, alongside 2x RGB LED strip headers. Above these is the M.2 slot featuring SATA 2x 10Gb/s speeds.
The X370 Killer SLI affords further expansion headers for: Front Panel Audio, COM port header, TPM header, Power LED and Speaker header, 2x USB 2.0 headers, 2x 4pin fan headers (one of which offers 1.5A power output for waterpumps)and finally a Clear CMOS Jumper.
Sitting just above the primary PCIe x16 slot is the Ultra M.2, A.K.A. M.2 NVMe 32Gb/s.
Above the top PCIe x1 slot there is a small M.2 slot dedicated for a WiFi/Bluetooth combo card.
The rear IO features a dedicated bracket for wireless antenna, 2x dedicated PS/2 ports for mouse and keyboard, a HDMI 1.4a port, 6x USB 3.1 Gen1, and a further pair of USB ports, 1x 3.1 Type A and 1x Type C, however due to the listed specifications we are unsure if these are Gen1 or Gen2 (the latter is likely). Finally, there there are 5x 3.5mm audio plugs supporting 8 channel audio, and microphone input as well as an optical SPDIF out.
The ASRock X370 Killer SLI features RGB lighting around the chipset heatsink, it provides a nice glow and features a few various effects allowing you to customise your systems appearance.