detect legacy/uefi

[silver310]

Hi, I've been successful in building snponly.efi and undionly.kpxe, and be able to boot them from a locally created DHCP server.
Now i want to implament this in our lab, but the DHCP team tells me they don't know how to configure the DHCP server to handle two PXE boot files (i've even send them a linux conf file and windows server 2012 guide on how to setup this), so now can only boot to 1 file.
Is it possible to somehow detect what arch the PC is booting with (EFI or Legacy bios), and then hand them the correct file?
I know i can use "iseq ${platform} efi", but i tried booting a legacy pc with undionly.efi and an EFI pc with undionly.kpxe and theu both just hang.
So is this even possible? or do i have to set this up at the DHCP server?

Also i'm having a hard time finding good documentation about iPXE build options and scripting docs, the examples at the site are minimal and don't really help.