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Index > OS Construction > Second-Stage Loader before File System?

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Joined: 22 Aug 2009
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RHaden 28 Aug 2009, 01:43
I'm starting this thread here because I still can't get into the Osdev forums. Mad

Anyway, I'm thinking about putting my second-stage loader before the start of the actual file-system structure (which will be based on the FAT). That way it will always start at the second logical sector and the boot loader doesn't need to understand the file system in order to load it. Does anyone see any major disadvantages to doing this? Please don't be afraid to speak out - by no means am I an expert here! Razz
Post 28 Aug 2009, 01:43
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When all else fails, read the source

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revolution 28 Aug 2009, 02:03
Well usually I am afraid to say anything here, but since you say "don't be afraid" then I will make a comment. Razz

Basically, it doesn't matter what you do when you start your OS. It all depends upon how you have structured it. If you find that putting a "second-stage" loader before something else to be useful to aid your development then go ahead and do it. You have nothing to lose by trying.

No one else can tell you that it is bad, or good, since no one else but you knows what your OS even does or how it works.
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cod3b453 28 Aug 2009, 13:15
I've also planned to do it that way both for simplicity and allowing me to have code to debug any FS problems.
Post 28 Aug 2009, 13:15
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Mac2004 28 Aug 2009, 13:43
Maybe this example helps you a bit?


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dosin 28 Aug 2009, 13:59
Second-Stage Loader before File System

If your using a floppy disk for testing.. should be fine only would cause a little less space on what all ready has limited space..

using a floppy disk every bit counts..

but you could code it to have a multi boot sys.. loads your OS on the floppy or if keypress load the mbr off the hd... but could all be done by removing the floppy..but would be good to learn how to boot your OS and how other OS boot..

For testing I made a multi boot system for a floppy but does not boot the floppy .. it boots the HD ... either windows or my os.. I am still working on a new file system..

but like rev... stated - its your os.. you are in control of how it loads..

but one advandage of just using the Fat is that other OS can read it..
so just copy and past your updated kernel and go .. versus using a tool to format every time you make a change.. your floppies will last longer..
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neville 29 Aug 2009, 02:12
Maybe it's not so much the OS but the particular application you're running that decides what is accessible. For example I use DEBUG a lot for reading and writing disk sectors. However all of the Microsoft versions of DEBUG supplied with MSDOS or Windoze are annoying because they refuse to access any media without a valid FAT and the so-called BIOS Parameter Block (BPB). They also check that their own "version" matches the OS version for no apparent reason other than to be a pain. I discovered that the DR-DOS version of DEBUG contains no limitations and is quite happy to read/write disk sectors on non-FAT disks, even disks without the BPB, and when running under any version of DOS or Windoze! Very Happy

An excellent 32-bit version of DEBUG, David Lindauer's "Get Real DeBugger" GRDB also has no such limitations when running under DOS. It even has support for Flat Real Mode and PCI bus access so I've used it extensively Cool

FAMOS - the first memory operating system
Post 29 Aug 2009, 02:12
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