With the changing business needs, you may need to add more expansion cards. That may not be possible in an already congested motherboard. Another thing is that the right PCI express slot may not be available for the type of additional expansion cards. PCI slots are valuable yet limited resources even in modern-day computers. So, should it be a bottleneck to the high performance that you want from your system?
Riser cards are independent circuit boards that can increase the number of PCI-express slots available on the motherboard. The Dell 1NH8H 2x8 riserfor PowerEdge, for example, avails three PCIe x8 slots from just one slot on a computer motherboard. It is an ideal choice if you need to extend a slot.
Expansion cards such as GPUs generate a lot of heat. If these units are stacked horizontally on the motherboard, the cooling can be a big problem. Riser boards are used to make it possible for a vertical component arrangement with enough space between additional expansion cards. So, cooling can be achieved efficiently.
Depending on the functionality of the system you want to extend, you might need x4, x8, or x16 PCI Express slots. Using a PCI e riser card makes it possible to get that slot with the bandwidth your application needs. The expansion card can then be plugged into the riser to scale-up performance and memory capacity.