PCIe cards you can install in your Mac Pro

Motherboards with a good number of PCIe slots pci e slot How to Enable a PCI Express Card Slot · 1 Open the BIOS menu · 2 Select the “Advanced” tab using the leftright arrow keys · 3 Select the “Video pcie 40 gpu in 30 slot PCIe slots allow your motherboard to connect with your PC's most critical components and provide key functionality

pcie 30 x1 slot You need to find a motherboard with built-in PCIE switch which automatically increase the price by a good margin See the MSi MEG X570S