It's part of a larger thing. It also controls what is booting.
Nope, the motherboard BIOS controls the boot, Int13
http://en.wikipedia.org/wiki/INT_13H controlled/controls it, when the disk specified as the boot disk, or attached to the specified channel is queried and told to lad the code at the location provided, which is where the operating system, or boot loader reside, and as its loaded the CPU starts to execute the code which once the kernel is up and in system memory, and its threads have loaded their machine configuration and or looked them up from BIOS memory tables, it starts to load the rest of the actual GUI and drivers.
Even on most UEFI systems a small section of the disk for boot it partitioned off as an acceptable boot partition, such as MBR on Windows, that contains the data required to start the actual software boot.
If you are curious get a Hex editor and look at sectors
http://en.wikipedia.org/wiki/Boot_sector and depending on how you look at it you can then determine what is being loaded.
But back to drive BIOS, how does it get transferred out of the PC to the NSA? By IP, and the OS and every major and customer hardware manufacturer is allowing this and not letting users see it? Or by some unknown pins even though people test and tweak systems and watch hardware input and output constantly? Or by voodoo magic?
Do I think it is happening? Yep
By the method described? Nope.
Specifically built hack firmware that is being released on machines built for use in some areas where they may not get access to others? Most likely.
Iran wants to buy servers, they have no manufacturing there, but Dell will sell them, and they report to the NSA or whoever about what they are selling, machines get loaded with a motherboard BIOS that allows low level access to the drives that the OS is unaware of, and either copies bits and pieces of the drive contents to a remote server, or causes corruption issues occasionally that they have to send techs in, or drives out and they are copied then.