There's an open source alternative to the BIOS implementations from the usual oligopoly: coreboot. See http://www.coreboot.org/ It's noteworthy to say that coreboot is not subject to the SMM exploits we've seen lately, for several reasons: - coreboot is not using SMM if there is not a significant reason to do it. - coreboot is doing the SMM entry on the non-poisonable ASEG rather than via TSEG or HSEG. Oh, and of course you don't have to break into the code to see what it does, because we don't feel that we have to hide coreboot's weaknesses.

Not many BIOSes actually protect BIOS write access through an SMI trap. There are a few more bios protection mechanisms though, like WP GPIO lines to the flash chip that can only be reset on a power cycle. So you'd need physical access for an attack.