Non-UEFI not finding PXE

So basically I have UEFI machines seeing and accepting PXE fine. They boot into OSD and deploy windows.

However non-UEFI (BIOS) based PCs do not see this at all. They simply scan for DHCP as Intel PXE usually does and then just skips straight through.

I am running all of these PCs within a Hyper-V environment. The server itself is a Gen 2 Hyper-V and the UEFI machine as well is Gen 2. The BIOS based machine is Gen 1. Other computers also have this issue and cannot see the PXE server and do not get a response.

This is a big issue as 90% of the computers onsite are BIOS based.

Any help would be greatly appreciated.

Thanks

Matt