did you try chip drivers/pci/onboard device pci a.0 on end register "rom_address" = "0xfff80000" #512k image end
or chip drivers/pci/onboard device pci b.0 on end register "rom_address" = "0xfff80000" #512k image end
etc...
let me know your HT_CHAIN_END_UNITID_BASE and HT_CHAIN_UNITID_BASE in Option.lb. also boot log in serial port.
YH
YH