You are going to need to look at a Threadripper CPU for this, the Ryzen lineup doesn't have enough PCIe lanes to support 4 GPUs. If you look for Threadripper CP

You are going to need to look at a Threadripper CPU for this, the Ryzen lineup doesn't have enough PCIe lanes to support 4 GPUs. If you look for Threadripper CPUs you will certainly find EATX boards with 4 PCIe slots.