UncoreInitPeim

Overview

UncoreInitPeim is the largest PEI module in the BIOS at ~1.35 MB, responsible for initializing the Intel Purley (Xeon Scalable) uncore -- the on-die logic outside the CPU cores including IIO (Integrated I/O), Ubox, Mesh, and Memory Controller. Spanning 136,806 lines of decompiled C split across 5 part files, it handles PCIe topology enumeration, memory RAS configuration, global MMIO resource allocation, and socket-level uncore register programming.

Key Functions

• UncoreInit -- Top-level uncore initialization dispatcher
• PcieAddressInit -- PCIe configuration space base address setup
• UsraRegisterFilter -- Unified System Register Access filtering for uncore registers
• DebugPrintDispatcher -- Debug/log output routing
• _ModuleEntryPoint -- PEI module entry; sets up debug services and dispatches sub-phases

Dependencies

• PCIe configuration space (mmcfg)
• PEI Services (PeiServices)
• USRA (Unified System Register Access) library
• Memory controller registers and HOBs
• IIO/Mesh topology descriptors

Platform

• Architecture: IA32 (x86, PE32)
• Subsystem: EFI Boot Service Driver (0x000B)
• Machine: 0x014C (i386)
• Entry Point: 0x395