# SaInitPei
**Index**: 0075 | **Size**: N/A | **Arch**: x64 | **Phase**: PEI

## Overview
SaInitPei initializes the System Agent (memory controller / uncore) during the PEI phase. It configures SA registers, sets up MMIO (Memory-Mapped I/O) ranges, and publishes system topology HOBs used by later DXE drivers.

## Key Functions
- System Agent base register initialization
- MMIO range programming
- PCIe root port configuration
- System topology HOB publication
- SA PM (Power Management) initialization

## Protocols / PPIs / Dependencies
- SA PEI PPI
- PeiServicesTablePointer PPI
- SystemAgent HOB

## Platform
HR650X (Purley platform, Skylake-SP)