"TPM is ready for use, with reduced functionality" message when the BIOS is in legacy mode with TPM 2.0
This article helps fix an error that occurs when you have the operating system installed in Legacy MBR mode (PC/AT) with Trusted Platform Module (TPM) version 2.0.
Applies to: Windows Server 2019, Windows Server 2016, Windows Server 2012 R2
Original KB number: 3123365
Symptoms
On a Windows Server-based operating system, you have the operating system installed in Legacy MBR mode (PC/AT) with Trusted Platform Module (TPM) version 2.0. In this situation, you receive a message in the TPM user interface stating that "The TPM is ready for use, with reduced functionality."
Resolution
On the operating systems that are listed in the Applies To section, TPM 2.0 is supported in UEFI mode only.
More information
TPM 2.0 is designed to be fully functional in UEFI mode. Systems must be in UEFI mode with TPM enabled and secure boot configured and enabled in order to attain the security status that's described in the following TechNet article:
Secure the Windows 8.1 boot process
For more information about secure boot and TPM, see the following resources:
Windows hardware certification requirements for Client and Server systems
Third-party contact disclaimer
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