Why is an operating system software loaded from hard disk than from a rom chip? [closed]

Question

Why is an operating system software loaded from hard disk than from a rom chip?

I was asked this question and I am unable to find the answer.

Can someone explain.

Thanks.

Answer 1

The easiest answer is ease of patching and extensibility. ROM cannot easily be patched - though with some permanent storage location and some creativity and foresight when building your initial ROM, you can patch it with some hook code.

Size of ROM isn't a great answer. CD/DVDs are a permanent location and could be used, though not ROM 'chips'. ROM chips can be made large enough to handle an OS (heck some versions of Linux fit on floppies not too long ago) and wouldn't be that expensive, though worse than a DVD for distribution costs.

Replacing an OS via a new ROM chip isn't that attractive, but if you just plugged in a new PCI card, would that be so bad? We do that already so this isn't a great argument either.

Access speed to a ROM chip, generally, will be much superior than to a harddrive so you would get a performance boost this way, so that's actually a plus. Also having a ROM makes it that much harder for malware to infect the OS - another plus.

So, in general, I see many pluses for a ROM based OS vs a RAM based one. Nice question.

Answer 2

An OS on a harddisk can be replaced by installing a new one onto that disk, and it can be easily updated.

If your OS is burnt into a ROM, that won't really work. Replace the OS?? Rip out the ROM chip and stick in a new one.... not a very attractive suggestion! (at least not for a desktop PC or notebook)

Answer 3

I guess iOS/Android is not loaded from a hard disk, so that depends.

Answer 4

Size and demand. Flash chips large enough to hold an OS that most people want/would want to run are ridiculously expensive.