From 01f38be30b806428057382138de08074b1c9b26f Mon Sep 17 00:00:00 2001
From: Kartikay Sharma <44971599+SharmaKartikay@users.noreply.github.com>
Date: Mon, 1 Jul 2019 16:48:14 +0100
Subject: [PATCH] Added Info on TPM 2.0 with Legacy \ CSM Mode

The info on the page lacks the complete info and this had led customer open a support cases with us where Bitlocker does not work when they have TPM 2.0 in legacy Mode. This Note will help readers get a complete rationale.
---
 .../information-protection/bitlocker/bitlocker-overview.md   | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/windows/security/information-protection/bitlocker/bitlocker-overview.md b/windows/security/information-protection/bitlocker/bitlocker-overview.md
index 138a9d5422..9b9350921a 100644
--- a/windows/security/information-protection/bitlocker/bitlocker-overview.md
+++ b/windows/security/information-protection/bitlocker/bitlocker-overview.md
@@ -60,6 +60,11 @@ A computer with a TPM must also have a Trusted Computing Group (TCG)-compliant B
 
 The system BIOS or UEFI firmware (for TPM and non-TPM computers) must support the USB mass storage device class, including reading small files on a USB flash drive in the pre-operating system environment.
 
+> [!NOTE]
+> TPM 2.0 is not supported in Legacy and CSM Modes of the BIOS. Devices with TPM 2.0 must have their BIOS mode configured as Native UEFI only. The Legacy and Compatibility Support Module (CSM) options must be disabled. For added security Enable the Secure Boot feature.
+
+> Installed Operating System on hardware in legacy mode will stop the OS from booting when the BIOS mode is changed to UEFI. Use the tool [MBR2GPT](https://docs.microsoft.com/en-us/windows/deployment/mbr-to-gpt) before changing the BIOS mode which will prepare the OS and the disk to support UEFI.
+
 The hard disk must be partitioned with at least two drives:
 
 -   The operating system drive (or boot drive) contains the operating system and its support files. It must be formatted with the NTFS file system.