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Question to real computer masters.

T

Thor_Sevan

Golden Member
Is it true that linux can bypass the bios ?

If an old HD isn't detected in the bios, can it be detected by Linux ??

A friend of mine it telling me that windows can't bypass the bios but Linux can. 🙂

I would like to understand this because I think that if the bios did not detected any HD, then it isn't possible by any operating system to detect it by itself.

Thor.
 
I am not 100% sure, but I am more towards you. If the bios can't detect it, that means the mobo doesn't know what's actually on the other end of the cable. I don't see how it is possible for the os to know about it then... I might be wrong.
 
Hardware initialization must be done by the bios, no other way. Beyond the post process, it boots from the O/S.
 
Software overlays work because the BIOS can already detect and access the HD, just not all the cylinders. The software overlay loads a new INT 13 routine so that the operating system can see the full drive capacity.

Modus
 
To my knowledge Windows can bypass the BIOS. I just tried it on my machine. In the BIOS I disabled my IDE Zip Drive. At boot the Zip was not detected yet in Windows my zip drive functions flawlessly. I do not have any drivers or software BIOS overlays. I am not sure if Linux can or not.
 
You've described a feature in Bios not the Bios
Just try disabling your IDE controllers and see if it will boot
 
NT-based OSes can also bypass some BIOS settings. If you try to hide partitions and/or drives, NT/2K will still see them.

-SUO

BTW, I don't know what rhymes with orange. 🙁
 
Drive overlays work by replacing the Master Boot Record on the drive and relocating the old Master Boot Record to a unused location on track 0. Then they replace the entry point to int 13 with the overlay code. If a request is made to read the MBR the Overlay intercepts and reads the relocated MBR.
 
Windows98 can do it. I've just installed Win98 a machine with:
Primary master - 6GB drive, just formatted
Secondary master - 1.2GB drive, partitioned to 500MB and 700MB
Secondary slave - CDROM

I tried to install Win98 on the pri. master (C🙂, but it said "Windows is already installed, you can't install this version" (it's an OEM version). Turns out that the 1.2GB drive had some old Windows on it, so I disabled it in "Standard BIOS setup". Installation went well, and on the "welcome to win98" boot, I saw:
C - 6GB drive
D - CDROM
E - 500MB partition
F - 700MB partition
All without touching the BIOS!
Afterwards, I re-enabled the drive in the BIOS, and it appeared as it normally would (C-6GB, D-500MB, E-700MB, F-CDROM).

-PJ
 
Modus,

Thanks for that info, I was wondering about a clarifaction on the matter. I happen to use a drive overlay, I use a Quantum Fireball+ LM 20.5GB on my 486 system (p83.. overdrive).

-RSI
 
No OS can override the BIOS until the boot process is to the point of reading from the disk, since no OS is loaded yet to do so! But once the boot process gets to the point of reading the Master Boot Record then it becomes possible to bypass or augment the BIOS (i.e. drive overlays).
 
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