Dynamic Root of Trust Measurement It's part of Intel's Trust Execution Technology https://en.wikipedia.org/wiki/Trusted_Execution_Technology This is basically what allows the hardware to verify that the OS which is being booted is "trusted".

Intel's TXT framework is quite nifty not fully utilized and I'm still it's not sure if it's as good as ARM's trust zone approach. The problem is that this is/will be a very important factor in any trusted computing in the future and currently it's utterly unaudited at least publicly (and from hearsay also wasn't internally audited).

Intel is pretty much mandating AMI/AMT support within the UEFI, support for TXT/TPM/NGSCB will be also mandatory soon unless Intel open sources all of this there will never be an open source UEFI BIOS which will functional with Intel going forward. Coreboot is shipped with proprietary parts which cover it, you can use Libre but then you are stuck with a decade old hardware and there is very little hope for it to ever support modern hardware the skill set way too demanding for an OSS project without a major corporate support and without full cooperation with Intel this wont be supported. If AMD was smart they would jump on this train, but as BIOS is quite a tricky business these days (probably even more complicated than OS internals with the exception of maybe really low level kernel stuff) I just don't think they want to take that risk considering their financial state.