Forcing legacy boot

I have a new PC with a reference Intel motherboard and AMI BIOS (5.010 on a LynxPoint-LP chipset motherboard). There is no OEM support, so I'm on my own with this.

I have a PXE network and WDS 2008R2 server that I'm using to deploy a Windows 10 image from. I have several PCs using a Realtek NIC, which PXE boot just fine. The new PCs are using an Intel 82574L NIC and they won't PXE boot. I have the option to select "UEFI: Intel 82574L Gigabit Network Connection" as the first boot device, but when I do, I see the message "Succeed to download NBP file", then it retus to the BIOS (I disabled all other boot devices). Unlike the guy who posted this screenshot: http://get-cmd.com/2015/02/21/sccm2012-r2-failed-to-boot-pxe-mode-nbp-file/, I do not see any information other than "Succeed to download NBP file".

I tried forcing the PC to boot in Legacy mode, but when I select "Legacy only" under CSM Configuration, the NICs not are listed as available boot devices. I also verified that the network port and cable are working correctly.

Looking at Intel's website (https://downloadcenter.intel.com/product/32209/Intel-82574L-Gigabit-Etheet-Controller), I don't see any utility for updating the firmware that would improve the situation.

What am I missing here? How can I make the BIOS boot from the NIC in Legacy mode?

Recent Questions...