Setting up SLI - NVIDIA SLI Performance Preview with MSI's nForce4 SLI Motherboard
NVIDIA's Quad-SLI Graphics Makes a Comeback - NVIDIA's 790i Arrives: SLI Rides Again
SLI requires motherboard support in order to work, meaning you need multiple pcie slots AND SLI support within the bios itself. If one were to connect a dual gpu card, such as
Gigabyte Z390 Gaming SLI Motherboard For 9th Gen Coffee Lake CPUs Breaks Cover | HotHardware