Stage IV finalizes silicon initialization, adds basic operating system required interfaces, and supports minimally featured operating system boot. The new components are support in a dedicated firmware volume.
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FvOsBoot | DXE/BDS Services | Yes | None |
FvLateSilicon | ACPI and SMM silicon support | No | FvOsBoot |
Which yields this example extension of the flash map for MMIO storage (add to Stage I + II + III map):
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Stage IV | FvOsBoot.fv | FvLateSilicon.fv (child FV) | ​ |
​ | ​ | Additional Components | Additional silicon initialization support that is performed late in the boot |
​ | ​ | AcpiTable.efi | Provides common ACPI services |
​ | ​ | PlatformAcpi.efi | Provides MinPlatform ACPI content |
​ | ​ | BoardAcpi.efi | Provides board ACPI content |
​ | ​ | PiSmmIpl.efi | SMM initial loader |
​ | ​ | PiSmmCore.efi | SMM core services |
​ | ​ | ReportStatusCodeRouterSmm.efi | SMM status code infrastructure |
​ | ​ | StatusCodeHandlerSmm.efi | SMM status code handlers |
​ | ​ | PiSmmCpu.efi | SMM CPU services |
​ | ​ | CpuIo2Smm.efi | SMM CPU IO services |
​ | ​ | FaultTolerantWriteSmm.efi | SMM fault tolerant write services |
​ | ​ | SpiFvbServiceSmm.efi | SMM SPI FLASH services |
​ | ​ | Additional Components | Additional post-memory components required for Stage IV boot |
See Appendix: Full FV Map for a more complete example Firmware Volume layout.