u-boot efi

I am trying to use u-boot-efi on a board that has an Intel D-1500 series processor and 64-bit UEFI ROM.
As per the information in doc/README.efi I built a u-boot-payload.efi with CONFIG_EFI_STUB_64BIT and installed it onto a USB drive I am booting with.
The UEFI loads/runs the u-boot but quickly goes into the weeds. I have very limited debug facilities as this is a 3rd party board. I was able to track down the failure to the following using calls to post_code():

lib/efi/efi_stub.c:efi_main()
lib/efi/efi_stub.c:jump_to_uboot()

     arch/x86/cpu/call32.S:cpu_call32()
       arch/x86/cpu/start.S:start()
         common/init/board_init.c:board_init_f_alloc_reserve() -> fails 

upon return.

This is the first "call" instruction after control is transferred to the start() of the 32-bit u-boot image.
I also tried adding a call to a do-nothing function and the results were the same (failure upon return).
The CPU goes the weeds and I guess it is in some exception code (no JTAG debugger available).

This is the first time I have used u-boot in this mode and my first time working with the x86 architecture.

Any suggestions would be most appreciated.

Thanks,
Scott