# Legacy8259

| Field   | Value |
|---------|-------|
| Index   | 0023  |
| Module  | Legacy8259 |
| Size    | 4,608 bytes (PE32+) |
| Phase   | DXE |

## Overview

UEFI DXE driver for the Intel 8259A Programmable Interrupt Controller (PIC). Manages legacy 8259 PIC hardware by providing an `EFI_LEGACY_8259_PROTOCOL` interface. Handles PIC initialization (ICW1-ICW4), interrupt masking via IMR, mode switching (legacy vs. virtual wire), IRQ-to-vector translation, and EOI signaling. Source: PcAtChipsetPkg/8259InterruptControllerDxe.

## Key Functions

- `_ModuleEntryPoint` -- PIC hardware init and protocol installation
- Interrupt masking, mode switching, EOI signaling
- IRQ-to-vector translation

## Protocols/Dependencies

- EFI_LEGACY_8259_PROTOCOL
- EFI_DEBUG_OUTPUT_PROTOCOL
- PCAT Compatibility Protocol
- Hardware: Master PIC (Cmd=0x20, Data=0x21), Slave PIC (Cmd=0xA0, Data=0xA1)

## Platform

HR650X Purley (PcAtChipsetPkg)