diff --git a/RTL8221B-app-note.md b/RTL8221B-app-note.md
index 021fd8ff..76ba59f9 100644
--- a/RTL8221B-app-note.md
+++ b/RTL8221B-app-note.md
@@ -1,3 +1,5 @@
+Warning! AI generated.
+
 The RTL8226B/RTL8221B SerDes Mode Setting Flow Application Note (Version 2.4) is essentially a "recipe book" for register writes. It moves away from the static descriptions found in the datasheet and provides state-machine logic that a driver must follow to ensure link stability.
 Here are the specific sequences covered in that document:
 
@@ -15,6 +17,20 @@ Since 10M, 100M, and 1000M traffic is physically sent over a 2.5G SerDes lane, t
 - The Flow: The document provides the exact values for 0x6F10 and 0x6F11 (usually 0xD455 and 0x8020).
 - Requirement: It details why the Rate Adapter must be enabled specifically when the MAC side is fixed at 2.5G but the Copper side is running at lower speeds.
 
+The Rate Adapter (RA) is the most critical logic block for 2.5G PHYs like the RTL8221B and RTL8226B when they are paired with a MAC (like your RTL9301) that is "locked" at a 2.5G SerDes frequency.
+
+Since the SerDes lane runs at a fixed physical baud rate (3.125 GHz for 2.5G), but the copper side might be linked at 10/100/1000Mbps, the Rate Adapter performs Bit Stuffing to fill the gaps. Without proper RA initialization, the MAC will see "garbage" data at lower speeds.
+
+According to the Application Note v2.4, the initialization must happen after the SerDes mode is selected but before the final SerDes reset is released.
+
+Step 1: Enable the RA Clock logic. You must tell the PHY to prepare the Rate Adapter buffers.
+
+Register: MMD 31, 0x6F10, Value: 0xD455 (This is a proprietary Realtek tuning value that stabilizes the internal FIFO depth).
+
+Step 2: Configure RA Mode and Speed
+
+Register: MMD 31, 0x6F11, Bit 15 (RA_EN): Must be 1 to enable the adapter, Bit 5 (RA_FIX_2500): Must be 1. This forces the Rate Adapter to always output 2.5G towards the MAC, regardless of the copper link speed. Value: 0x8020 (Standard for most 2.5G designs).
+
 Thermal Sensor Calibration and Monitoring
 
 The Application Note provides the "Enablement Flow" that is often missing from the generic datasheet: