master boot record 
Author Message
 master boot record

whats the difference between the Master Boot Record and the Boot Sector...
my book seems to be talking about two different things


Thu, 15 Nov 2001 03:00:00 GMT  
 master boot record

Quote:

>whats the difference between the Master Boot Record and the Boot Sector...
>my book seems to be talking about two different things

MBR has to do with the physical disk. Boot Sector has to do with
partitons and OSes.

There is only one MBR for a physical hard drive. It does contain both
booting code, and data about partitions.

Each bootable partition in the disk has its own Boot Sector. This one
contains system files for the OS which owns the partition (for
instance, MSDOS' io.sys & msdos.sys files)

There may be more than one bootable partition in a single physical
drive, each with its own boot sector. But only one of those partitions
is active at a time.

On boot up, BIOS makes his own things, and then searches for a MBR in
the disk. If found, controll is passed to the program which is stored
in the MBR. The MBR program checks which partition is the active one,
and, in turn, gives control to the system files in the Boot Sector of
that active partition, which load the OS.

So the MBR affair is to launch the OS Boot Sector which is active at a
time. There are programs (LILO, forinstance, though this may be also
located elsewhere) which install themselves in the MBR, thus acting as
launchers. On Boot Up, BIOS passes control to this MBR programs, which
show you a menu from which you may select which one is to be the
active partition. Upon selection, the launcher activates that
partition, and gives control to the system files in it (in the
partition's boot sector).
Manuel Algora



Fri, 16 Nov 2001 03:00:00 GMT  
 master boot record

Ehh, the master boot record is sector 0 of your (hard)disk. It is loaded as
a bootsector by BIOS...

The bootsector program CAN however be a bootloader. In this case, a
partition table is used (which could be anything, but they use a standard
format so OS/2, Windows and linux can coexist).

This bootloader then loads a partitions first sector, and fools the
bootsector which will think it was booted (while it was simply loaded by the
real bootsector).

Just remember that partition tables and all are a software thing, no BIOS or
hardware forces you to use partitions. You could even make up your own
partition format and all, which won't be compatible with FDISK and LILO !!
But who would wanna do that....



Mon, 19 Nov 2001 03:00:00 GMT  
 master boot record


In newsgroup: alt.lang.asm

Quote:

> Just remember that partition tables and all are a software thing, no BIOS or
> hardware forces you to use partitions. You could even make up your own
> partition format and all, which won't be compatible with FDISK and LILO !!
> But who would wanna do that....

Actually, LILO doesn't care (FDISK does, but you could write your own
for your new format).  Linux, for example, speaks at least four
different partition table format: DOS, BSD, UnixWare and Mac.

        -hpa
--
"The user's computer downloads the ActiveX code and simulates a 'Blue
Screen' crash, a generally benign event most users are familiar with
and that would not necessarily arouse suspicions."
-- Security exploit description on http://www.zks.net/p3/how.asp



Tue, 20 Nov 2001 03:00:00 GMT  
 master boot record
Do you know where I can find ASM source for a formatter that uses INT 13H?
I have some that uses INT21H, but I'm writing an OS, so my prog won't be
running on MS-DOS.



Quote:


> In newsgroup: alt.lang.asm

> > Just remember that partition tables and all are a software thing, no
BIOS or
> > hardware forces you to use partitions. You could even make up your own
> > partition format and all, which won't be compatible with FDISK and LILO
!!
> > But who would wanna do that....

> Actually, LILO doesn't care (FDISK does, but you could write your own
> for your new format).  Linux, for example, speaks at least four
> different partition table format: DOS, BSD, UnixWare and Mac.

> -hpa
> --
> "The user's computer downloads the ActiveX code and simulates a 'Blue
> Screen' crash, a generally benign event most users are familiar with
> and that would not necessarily arouse suspicions."
> -- Security exploit description on http://www.zks.net/p3/how.asp



Tue, 20 Nov 2001 03:00:00 GMT  
 master boot record


   >Do you know where I can find ASM source for a formatter that uses
   >INT 13H? I have some that uses INT21H, but I'm writing an OS, so my
   >prog won't be running on MS-DOS.

ftp://oak.oakland.edu/pub/simtelnet/msdos/dskutil/llfmt.zip

.....................................................................
Return address is mangled to foil spambots. Remove all "g"s to e-mail.

Net-Tamer V 1.08X - Test Drive



Wed, 21 Nov 2001 03:00:00 GMT  
 master boot record

Quote:
>Actually, LILO doesn't care (FDISK does, but you could write your own
>for your new format).  Linux, for example, speaks at least four
>different partition table format: DOS, BSD, UnixWare and Mac.

I mean that if you use another partitioning format, lilo can only boot MBR's
from harddisks, but not the bootloader from your partitions (unless you
extend lilo with your partitioning format).

But he, if you're writing MBR's and all, you could buy a old 486, and do it
on that. It will take year(s) for you to be able to demand a FASTER computer
for your freaking...

Anyway, my little OS (does everyone has one here ??) just boots itself from
the MBR, and ignores any partitioning !! So no dual-boots !!



Sun, 25 Nov 2001 03:00:00 GMT  
 master boot record
[snip]

Quote:
>Anyway, my little OS (does everyone has one here ??) just boots itself from
>the MBR, and ignores any partitioning !! So no dual-boots !!

  This may be off-topic, but now that you mention it, where can I find a
good tutorial on making OS's? I don't necessarily want sources to OS's, but
the theory behind the making of an OS. Are there any good sites (or books)
with this info? Thanks in advance!

--
Jessie
"With great power comes great responsibility"



Sun, 25 Nov 2001 03:00:00 GMT  
 master boot record
I am beginning to think that we should all focus on one BIG OS, I don't know
about Linux or whatever, but if everyone (me included) wants to or has made
his/her own OS, wouldn't working together help a lot more than everyone
having their own personal, non-portable, incompatible, one?  I guess
COMMENTING - yes, the dreaded REM statements from your C64 - is going to be
the most helpful.  Everyone's going to come into the project at a different
stage, and need to learn from the MBR up.  Would it be inappropriate for
everyone to group up, and post what they have available...maybe get a
website going with everyone's stuff on it...don't know who should be the
leader and maintain it, but the idea's sound and should be discussed.
Everyone should agree that info is hard to find, so let's put it all in one
spot, and get the word out, eh?


Quote:

> [snip]
> >Anyway, my little OS (does everyone has one here ??) just boots itself
from
> >the MBR, and ignores any partitioning !! So no dual-boots !!

>   This may be off-topic, but now that you mention it, where can I find a
> good tutorial on making OS's? I don't necessarily want sources to OS's,
but
> the theory behind the making of an OS. Are there any good sites (or books)
> with this info? Thanks in advance!

> --
> Jessie
> "With great power comes great responsibility"



Mon, 26 Nov 2001 03:00:00 GMT  
 master boot record
This is a great idea, please try to make it become true. I'll love it to help
with a new OS. I want to begin in S myself, but why not with more people like
you said.
Super.

Thomas

Quote:

> I am beginning to think that we should all focus on one BIG OS, I don't know
> about Linux or whatever, but if everyone (me included) wants to or has made
> his/her own OS, wouldn't working together help a lot more than everyone
> having their own personal, non-portable, incompatible, one?



Wed, 28 Nov 2001 03:00:00 GMT  
 master boot record
I am also trying to make an OS i think the website is a good idea seeing as how
assembly is going downhill with all the high level VB VC++ and such
www.anexa.com has free discusion web pages we could create one and share files
and stuff on that.

   Dustin



Sat, 01 Dec 2001 03:00:00 GMT  
 
 [ 11 post ] 

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