Force legacy mode PXE in IBM system X(xSeries) server

The Unified Extensible Firmware Interface (UEFI) tends to replace the basic input/output system (BIOS) of x86 personal computer.
Intel Corporation developed EFI in the mid 1990s to enable the Itanium class of processors without having to implement legacy processor operating modes that are required by BIOS
Later, the UEFI Forum Inc. was formed by Intel, IBM, Hewlett-Packard, Dell, Apple, and other
companies to turn EFI into a industry standard that is appropriate for broader use on other
architectures, including x86 and x64.
Today, UEFI is becoming widely accepted throughout the industry, and many systems are
making the transition to UEFI-compliant firmware.  The list of Vendors using UEFI:
http://www.uefi.org/news/uefi_industry/UEFIEvaluationPlatforms_2011_05.pdf
PXE on UEFI
UEFI PXE uses a special boot file (install media/boot/efi/EFI/redhat/grub.efi) rather than the traditional boot file “pxelinux.0”. If you have an existing PXE provision system and don’t want to change it to meet UEFI PXE requirement, you can force legacy mode PXE.
Force legacy mode PXE in IBM system X(xSeries) server
System Setting -> Boot manager-> add boot option
add "legacy only".
System Setting -> Boot manager-> change boot order
Move "legacy only" option above the device (PXE network):
  legacy only
  PXE network
The system will boot PXE in legacy mode automatically, If you want to boot from PXE netowrk manually after pressing F12 , select legacy only not PXE network.
Each network adapter also has PXE mode switch, the options are UEFI, Legacy, Both, or None. But forcing  legacy mode here has doesn’t seem to work.