NVIDIA GeForce RTX 3090 is a 3-slot graphics card : r/AMD_Stock
GPU 101 - Part 1 - Integrated vs Discrete Graphics Hardware | ZOTAC
Amazon.com: Vertical GPU Mount for 3 Slot and 2 Slot GPUs, PCI E 3.0 X16 Graphics Card Bracket for ATX PC Case, Magnetic Desktop Graphics Card Holder (26 * 6.2 * 12.8 cm) : Electronics
motherboard - Positioning triple slot graphics cards - Super User
motherboard - Positioning triple slot graphics cards - Super User