Do I get this right, you are trying to boot your HP server as a client via PXE to be cloned?
Do you see any error messages when trying to boot via PXE? Without that we won’t be able to help.
Seams like others have achieved booting from a Broadcom NetXtreme II NIC https://forums.fogproject.org/topic/3949/ipxe-problems-with-broadcom-netxtreme-ii