not in ohio
reply to koitsu
Re: MBR vs /boot Kids today, huh? That's how bootstraps always worked - it's why they're called 'bootstraps'. Each stage gets a little more capability, but it's quite a long way before you get to be able to support a filesystem.
You missed out the code that reads in the first 512 bytes of mass storage. Luxury computers have that in ROM of some kind, otherwise you have to enter it through console switches. Regardless, that's the first stage of bootstrap. I recall the PDP11/40 primary boot was round about a dozen 16-bit words.