Can OS bypass the BIOS?

[Mario F.]

http://computer.howstuffworks.com/bios.htm

[siavoshkc]

Mario, have you read it yourself? It doesn't answer my question. But in one place it says

The device drivers are other pieces of software that identify the base hardware components such as keyboard, mouse, hard drive and floppy drive. Since the BIOS is constantly intercepting signals to and from the hardware, it is usually copied, or shadowed, into RAM to run faster.

It means these driver remain in memory even after OS loads? So OS can use its methods, right? Can OS overwrite these methods?

[Mario F.]

No. I haven't read it. I just know the information to be correct. If it doesn't answer your question then I'm afraid I misunderstood it. I thought you were asking how the bios operated.

As for your last question, yes. At least that is how it used to be with the 16 bit systems when I had a better understanding of how the OS and BIOS interacted. Some drivers where shadowed into RAM for easier and quicker access. And this shadowing mechanism could be configured in the BIOS itself.

These "new" operating systems are a new ball altogether though. PnP for instance, can (and will) remap device drivers IRQs. So, I cannot say exactly how it works these days.

What I am surpised though is with two things...

. How this whole conversation steamed from installing linux. Especially when we are talking here of such a common and easy to use distro.

. And why do you insist Fedora Core 5 can use a driver you have disabled in your BIOS.

[siavoshkc]

No. I haven't read it. I just know the information to be correct. If it doesn't answer your question then I'm afraid I misunderstood it. I thought you were asking how the bios operated.

Thanks for the link, but it was better to fully understand the question first.

How this whole conversation steamed from installing linux. Especially when we are talking here of such a common and easy to use distro.

This thread not because I can't install that common easy to use ditro (I have started a seperate thread for it in general board because I am in a big trouble with it). Its just because I was puzzled and I want to know about BIOS duty when OS is running.

And why do you insist Fedora Core 5 can use a driver you have disabled in your BIOS.

Strange, I didn't insist in anything and I didn't talk about driver.
I just said Fedora detects both HDDs while I've disabled one of them. It is a fact. Till now I thought OS can read HDDs and some sorts of hardware by using BIOS. But when I saw that fact, that Linux detected that disabled HDD, I searched in my head and when I collected all my knowledge, I saw two things. First I saw OS don't really need BIOS for some task as it can do them itself. Second, I saw that there is a lack of knowledge about this object in my brain (One of that valleys). I don't know what tasks are done by BIOS when OS is running. I have never thought about that actually.

[itsme86]

I still have a hard time believing that linux is finding a harddrive that's disabled in your BIOS:
http://dirac.org/linux/boot/

The first part of booting involves running code stored in the computer's ROM (Read Only Memory). This code is called BIOS (Basic Input/Output System). BIOS has only two functions:

1. Memory and device detection and diagnostic checks (also known as "posting")
2. Loading a bootstrap program from the boot disk into memory. This bootstrap program will eventually load the operating system.

Device detection and configuration
One of the kernel's first jobs is to check out the system and see what hardware is present. When you compiled the kernel, you told it about what devices it should expect to find. Upon starting, the kernel tries to locate and initialize each device you told it about. Here is an example of my kernel looking for the printer that I configured:

parport0: Printer, Hewlett-Packard HP LaserJet 6MP

Device information at this point is usually underspecified so the kernel tires to determine the other information it needs by probing the bus for devices and asking the appropriate drivers for information. The drivers for devices that are missing or that don't respond to a probe are disabled. Even if a device is later connected to the system, it will not be accessible to unix processes until the machine has been rebooted.

[itsme86]

Also found this here: http://www.debian.org/releases/stabl...h03s06.html.en

3.6.3.4. Shadow RAM
Your motherboard may provide shadow RAM or BIOS caching. You may see settings for “Video BIOS Shadow”, “C800-CBFF Shadow”, etc. Disable all shadow RAM. Shadow RAM is used to accelerate access to the ROMs on your motherboard and on some of the controller cards. Linux does not use these ROMs once it has booted because it provides its own faster 32-bit software in place of the 16-bit programs in the ROMs. Disabling the shadow RAM may make some of it available for programs to use as normal memory. Leaving the shadow RAM enabled may interfere with Linux access to hardware devices.

[itsme86]

And I found this at this errrrr, extravagant, website: http://www.ibiblio.org/pub/linux/doc...1/SSR01-07.htm

The BIOS is the initial program, on the system boards ROM's. DOS uses it to access the hardware, Linux doesn't use it, except to boot-strap-load the kernel.

[Mario F.]

Thanks for the link, but it was better to fully understand the question first.

You are really something, aren't you?
I'll suggest in turn, you first do some research before asking. That way you will be able to better put your question or have it answered before having the need to post. How about that?

I don't have to be guessing what you really mean with your question when little of it makes any sense.

[Mario F.]

And I found this at this errrrr, extravagant, website: http://www.ibiblio.org/pub/linux/doc...1/SSR01-07.htm

That except, is a big except.

http://linuxgazette.net/issue70/ghosh.html

[itsme86]

That except, is a big except.

http://linuxgazette.net/issue70/ghosh.html

But still, I'm just referring to the device detection stuff. I still don't see how the BIOS can load the bootstrap information that's in the first sector of a harddisk that's disabled in the BIOS, but whatever

[siavoshkc]

I still don't see how the BIOS can load the bootstrap information that's in the first sector of a harddisk that's disabled in the BIOS

It is not true in my case. Linux setup (Anaconda) read the HDD.

[CornedBee]

No, there's absolutely no conflict of statements here.

Linux, once loaded, will completely ignore the BIOS and instead rely on its device drivers to probe and detect the hardware. If you disabled a device in BIOS, Linux will not care. Thus, Anaconda will not care.

If you disable the HDD Linux is installed on, however, it will never get loaded. But that's not the case here: I presume Anaconda is running from an installation CD, right?

[siavoshkc]

No, there's absolutely no conflict of statements here.

Linux, once loaded, will completely ignore the BIOS and instead rely on its device drivers to probe and detect the hardware. If you disabled a device in BIOS, Linux will not care. Thus, Anaconda will not care.

So, does this mean Linux never uses BIOS during the entire process of "bootstrapping"? Well, the answer is No, Linux is forced to use BIOS in the bootstrapping phase when it has to retrieve the Kernel image from disk or some other external device.

This is before loading Linux, after that BIOS is completely ignored. Intresting!

[edit]

You are really something, aren't you?
I'll suggest in turn, you first do some research before asking. That way you will be able to better put your question or have it answered before having the need to post. How about that?

I don't have to be guessing what you really mean with your question when little of it makes any sense.

First I did some searching. Second my english is not as good as you, ask me to explain more if questin was vague.


Subhasish Ghosh is as old as me (1 year older), but his (her) knowledge is three times more than me, intresting too!

[VirtualAce]

Can OS bypass the BIOS?

Yeah it's called x86 protected-mode.

[siavoshkc]

I read somewhere that some OSes have to use BIOS calls for ACPI.