This is older generation card designed for PCIe v2 standard but your H470 chipset is operating on PCIe 3.0Even though PCIe v3 slots normally are backward compatible with PCIe v2 cards - probably it's just some incompatibility issue on specific config by Dell.What chipset is running on your another machine where this card works?Also have you tried this card in all slots? (XPS 8940 has 3 PCIe slots: x1, x4 running via PCH and Blue x16 hooked directly into CPU lanes, although it is dedicated to graphics - sometimes other cards do work there too {at least on other non-Dell machines}).
Card: 2 Port SATA 6 Gbps PCI Express eSATA Controller Card BIOS Version: 2.10.0I cannot get this machine to recognize this card in the BIOS or within Windows.  I have not tried another card, but the card works on another machine. I've already performed the steps here, but that seems like the card must already be recognized to get this far.   Thanks in advance!
XPS 8940, not recognizing PCIe eSATA controller card