Edit: 2020-09-09 – HPE clarified that they are doing this in a different manner than Dell after initially confirming that they were using the AMD PSB feature. After this went live, HPE sent us the following:
HPE does not use the same security technique that Dell is using for a BIOS hardware root of trust. HPE does not burn, fuse, or permanently store our public key into AMD processors which ship with our products. HPE uses a unique approach to authenticate our BIOS and BMC firmware: HPE fuses our hardware – or silicon – root of trust into our own BMC silicon to ensure only authenticated firmware is executed. Thus, while we implement a hardware root of trust for our BIOS and BMC firmware, the processors that ship with our servers are not locked to our platforms. (Source: HPE)