Yes, you can use a second GPU slot with your X570 tuff gaming setup.
Yes, you can use a second GPU slot with your X570 tuff gaming setup.
This question prompts reflection on the reasons behind self-limiting beliefs.
It differs from machine to machine and system to system, and sometimes between CPUs (like the X99 platform where the 5820K has only 24 PCIe lanes while higher-end models offer 40). However, as you mentioned, the manual clearly states that the second slot is 16x, which should eliminate any confusion. If the second slot interacts with components such as an M.2 drive or SATA ports, the manual will specify this too.
you might want to do that because it helps avoid overloading the system, even though it doesn’t seem like a big issue with 8x. running at 16x on the second slot usually depends on the hardware design, similar to how lower slots have limited bandwidth in certain architectures.
I haven't come across a manual that doesn't mention this somewhere. It often explains how performance changes based on the drive type, mentioning speed differences between PCIe and other interfaces. It might also note that certain slots are disabled or resized to accommodate different drive sizes.