Windows floppy question.
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Thread: Windows floppy question.

  1. #1
    Junior Member
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    Windows floppy question.

    I have noticed that Windows will only format a disk for 1.38mb. Why is this? I am needing to put a boot image onto a cd and for the life of me it will not fit! It is 1.40mb, just a tad larger than what the disk can hold. It is frustrating b/c the all the disks are supposedly 1.44. Is all this space taken up by the filesystem on it or what? Any help will be appreciated.

    Exitrial

  2. #2
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    Exitrial, "all that space" is only 6/100 of a meg!

    Anyway, it is the file system that takes up that little bit.

    File system overhead varies. For example, you cannot format a 1.44MB floppy with NTFS due to the amount of space the filesystem itself takes up.

    Vegas
    Put down the mouse......Step away from the keyboard!
    --Me

  3. #3
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    It is FAT(I think) not NTFS, I am using Windows 98. That is why I don't understand it. Do you think maybe doing this under Linux would allow me to put the boot image on the floppy disk?It is just really frustrating.

    Exitrial

  4. #4
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    Honestly not sure about Linux file system. I imagine you are using FAT.

    My comment re:NTFS was to illustrate the overhead used in formatting various file systems. You could not format a floppy with NTFS even if you wanted to, due to the overhead involved.

    Cheers,
    vw
    Put down the mouse......Step away from the keyboard!
    --Me

  5. #5
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    A newly formatted floppy with the default settings has 1,457,664 bytes free.

    That is about 1423.5k bytes
    and if 1Mb == 1024k
    then it's

    1.3901 Mb

    Now we can increase that in several ways: I'm using the linux "mkfs.msdos" program as it has more flexibility than the (MS) DOS format.com program:

    1. The default number of FATs is 2 - we can decrease that to 1 and the disc will still work.
    2. We can increase the number of sectors per cluster - this reduces the size of the FAT as there will be fewer clusters hence fewer entries in the FAT. The default is 8 sectors, if we increase this to 16, we get a bit more free space.
    3. We can decrease the number of root directory entries. The default is 112 but the minimum is 16. We can of course then only have 16 files in the root directory, but I'll assume that's ok.

    If we combine all these techniques, we can get from 1457664 bytes to 1466368 bytes free - that is a whopping 0.5% increase in space (or about 8k more)

    Note that this is only the optimum for storing a single large file. Because we increased the cluster size and decreased the directory entries, small files will now take up more space on average, and we will be able to have fewer of them.

  6. #6
    str34m3r
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    I hope you'll forgive me, but I'm going to dodge the question a bit. You said that you were trying to put a boot image onto a floppy. Well, copying the file onto the floppy won't do what you want it to do. What you really need to do is to do a raw write to the floppy. Most linux CD's come with a program call 'rawwrite' which writes the entire image (filesystem and all) to the floppy bit by bit. This means that every single bit of the floppy is used. In linux, the 'dd' command allows you to do the same thing. You just type 'dd if=floppyimage of=/dev/fd0' and it writes the disk from scratch. I hope this helps, even though I dodged the question you actually asked.

  7. #7
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    just like water off a duck\'s back... I AM HERE.

    for CMOS help, check out my CMOS tut?

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