Hi, When booting UefiPayloadPkg in my system (x86 Denverton SoC, coreboot) an assert error is generated in the PciHostBridgeDxe driver. In the InitializePciHostBridge() function if all ASSERT's are ignored (by commenting out the code) the boot can move further on until it reaches the UEFI Shell. Any clues? Loading driver at 0x0007EE61000 EntryPoint=0x0007EE6CF52 PciHostBridgeDxe.efi InstallProtocolInterface: BC62157E-3E33-4FEC-9920-2D3B36D750DF 7EF1F698 ProtectUefiImageCommon - 0x7EF1F140 - 0x000000007EE61000 - 0x0000000000013000 SetUefiImageMemoryAttributes - 0x000000007EE61000 - 0x0000000000001000 (0x0000000000004008) SetUefiImageMemoryAttributes - 0x000000007EE62000 - 0x0000000000010000 (0x0000000000020008) SetUefiImageMemoryAttributes - 0x000000007EE72000 - 0x0000000000002000 (0x0000000000004008) PROGRESS CODE: V03040002 I0 InitRootBridge: populated root bus 0, with room for 7 subordinate bus(es) RootBridge: PciRoot(0x0) Support/Attr: 10003 / 10003 DmaAbove4G: No NoExtConfSpace: No AllocAttr: 0 () Bus: 0 - 7 Translation=0 Io: 0 - 4FFF Translation=0 Mem: D4000000 - FE0FFFFF Translation=0 MemAbove4G: FFFFFFFFFFFFFFFF - 0 Translation=0 PMem: FFFFFFFFFFFFFFFF - 0 Translation=0 PMemAbove4G: FFFFFFFFFFFFFFFF - 0 Translation=0 PciHostBridgeDxe: IntersectMemoryDescriptor: desc [E0000000, F0000000) type 1 cap 870000000002600F conflicts with aperture [D4000000, FE100000) cap 1 ASSERT_EFI_ERROR (Status = Invalid Parameter) ASSERT [PciHostBridgeDxe] /home/lxuser/occ/edk2/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostBridge.c(488): !EFI_ERROR (Status) Thanks, Sumo