Common reasons for updating firmware include fixing bugs or adding features to the device. This may require ROM integrated circuits to be physically replaced, or flash memory to be reprogrammed through a special procedure... Firmware such as the program of an embedded system may be the only program that will run on the system and provide all of its functions.... The BIOS may be "manually" updated by a user, using a small utility program.... proprietary firmware as a security risk, saying that "firmware on your device is the NSA's best friend" and calling firmware "a trojan horse of monumental proportions".
Anyways, not much is said about how the firmware actually gets added or updated, and it all seems like a black box.
I am interested to know in more detail how the BIOS system gets installed on the "system board":
The BIOS firmware comes pre-installed on a personal computer's system board [wondering how], and it is the first software to run when powered on.... Most BIOS implementations are specifically designed to work with a particular computer or motherboard model, by interfacing with various devices that make up the complementary system chipset. Originally, BIOS firmware was stored in a ROM chip on the PC motherboard. In modern computer systems, the BIOS contents are stored on flash memory so it can be rewritten without removing the chip from the motherboard. This allows easy, end-user updates to the BIOS firmware so new features can be added or bugs can be fixed, but it also creates a possibility for the computer to become infected with BIOS rootkits. Furthermore, a BIOS upgrade that fails can brick the motherboard permanently, unless the system includes some form of backup for this case.
Basically this question is, what actually happens to get the software onto the hardware in this case. In my head I am imaging a laser engraver engraving the software into the metal somehow. That is as much as my knowledge goes, which is probably wrong. So I would like to know how to get it on there, how you install something without even the BIOS system being available to help you bootstrap your hardware.