Some motherboards just have a physical jumper that prevents BIOS flashing. This happens infrequently enough as to warrant it for one server, or 10 servers, or maybe 100 servers. Likely unpractical for 1000 servers though.
https://www.servethehome.com/the-ocp-dc-scm-hff-is-taking-ov...
Make this one simple enough and add an EPROM for it. Effectively a security chip for the oob. Extra points for secure enclave-like verified boot.
These days it’s common to do firmware updates to address small issues or even support the new CPU that was launched after the motherboard was manufactured.
I could see manufacturers adding a write-protect physical switch for those who want it. Make it opt-in and toggleable.
> Often we see.. great security.. compromised by other great ideas for mgmt and other things.. starts to weaken its security posture.. want to keep Caliptra very clean [via OSS firmware transparency]
Using the method you talk about would mean that this kind of update wouldnt be possible, 99% of users would never toggle with a switch to update firmware.
This would be a huge burden in the server world too, to unrack flip switch, update, revert switch re-install.
I assume you mean specifically motherboard firmware updates, because firmware updates are actually pretty common, for most server grade motherboards vendors ship updates about every other month[1].
1. https://git.kernel.org/pub/scm/linux/kernel/git/firmware/lin...
I think these days, the stub "BIOS flashback" is the trendy thing, where you can plug a flash drive into a magic slot and press a button to flash without even having a CPU installed.
This offered the same "brick-resistance" feature with the added benefit that people weren't stuck if they tried to pair an old-stock mainboard with a new CPU that wasn't supported by the original firmware release.
TBH, I'd rather they go the complete opposite direction: replace the soldered EPROM with a SD slot and a $1 MCU that reads the card and emulates a ROM chip. That could be configurable to write-protect the card, or you could just trivially swap it if you didn't trust the firmware image for any reason, while avoiding the fumbliness of modern tiny 8-pin flash chips. You could socket a big old-fashioned DIP ROM, but will people feel comfortable even trying to pry that out of a $10,000 server even with the appropriate chip puller tool?