Questions about the BIOS

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Rhapsody
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Joined: 2013/09/17

Situation :
I've been trying to get a better understanding of what the BIOS does for the system after the OS is loaded. I've been told that the BIOS remains the entire time that the system is on, but I haven't yet figured out why.

I was reading this page :
( http://www.bioscentral.com/misc/biosbasics.htm# ),
which gave me the impression that the BIOS might still be necessary for establishing interactions with certain peripheral devices, like plug and play devices. The page says that, during the configuration of a plug and play device, "the BIOS calls upon specific features of a plug and play expansion board" so that it can help to configure the device.

I was always under the impression that a plug and play device would contain it's own built-in drivers, that would enable it to interact with the OS via some plug and play/hardware port protocol. In which case, the BIOS shouldn't really be necessary to configure the device.

I'm curious about this because, it seems to me that having the BIOS operational throughout the duration of the system's use, is actually a major security flaw. If the BIOS is running, and if the system is connected to a network, then it should theoretically be possible to access the BIOS from the network. Whereas, if the BIOS were off, and the control of it's state was inaccessible to the OS - wouldn't that be a lot more secure?

So here are my questions :
> Why would the BIOS be necessary to configure a plug and play device? Wouldn't it be more effective and secure to include drivers in the plug and play device, itself?
> What functions does the BIOS perform after the OS is loaded?
> Do all systems continue to run the BIOS after the load of the OS?
> How do you disable the BIOS? Would you be able to disable it specifically after the load of the OS?

And I have many more of course, but those will do for now!
If anyone knows any information about this, or has any research resources relative to this topic, I would really appreciate your response!

Thanks!
- Rhapsody

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Update :
EarlMate, your answer was awesome! If I had "karma" I'd vote for it!
These links were very useful, especially that last one!

For anyone who is interested in this topic, here is what I found from this link in regards to the tasks that the BIOS performs :
- modifying the CPU and bus clocks
- enabling/disabling mainboard devices
- expansion port power control
- suspend-to-disk and suspend-to-RAM
- resume event settings

In particular, the BIOS seems to be uniquely responsible for the "STR" mode (which is a type of sleep mode?) :
"Suspend-to-RAM can not be implemented by the OS, as it relies on the BIOS skipping the RAM initialization and test, so the OS needs an API to tell the BIOS that it intends to be resumed with the current RAM contents. In order to provide this service, the BIOS asks the OS to leave a certain RAM area intact."

Again - from the linke EarlMate provided.
Thanks so much for that!
- Rhapsody