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Thread: Segment:Offset pains...

  1. #1

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    Hyperactive Member Warmaster199's Avatar
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    Question Segment:Offset pains...

    Greetings fellow ASM programmers,

    I am having a sort of problem with a start-up code that I'm making. I have a bootsector that works perfectly. It searches the FAT on a disk's root for a file name, then it reads the file into memory and jumps to it.

    The start-up code is located in 0x0050:0x0000, and the boot sector is loaded into 0x07C0:0x0000 (OR is it 0x0000: 0x07C0???)

    Now, I need to know what is wrong, because I CANNOT access the MBR that's in the bootbloc which is in memory. It is VERY frustrating for me. I have been trying for about 3 days to get the start-up code to access the MBR so I can try to load another file... Changing a single thing then assembling, then going into my other room to my 486, I boot it up and the 486's BIOS says:

    NO ROM BASIC
    HANGING SYSTEM

    It is REALLY bothering me now... NASM doesn't seem to be bothered, it assembles nicely, but it really doesn't execute correclty...

    This is TOTALLY REQUIRED for my OS to work. I HAVE to have a startup file because the bootsector code is too big to fit A20 enabling code (98 bytes), so I can't load the kernel(It could be several megs of executable code!!! - I expect the start-up code to be around 1 or 2KBytes).
    Designer/Programmer of the Comtech Operating System(CTOS)

  2. #2

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    Hyperactive Member Warmaster199's Avatar
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    Sorry, I forgot this:
    Attached Files Attached Files
    Designer/Programmer of the Comtech Operating System(CTOS)

  3. #3

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    Hyperactive Member Warmaster199's Avatar
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    Now, I have figured it out. I didn't take into account that the oemID is 8 bytes long.

    There STILL is a problem:
    The Image kernel.bin is a very simple kernel that displays a message and hangs. The image file does not get loaded into memory... The system just freezes.
    Designer/Programmer of the Comtech Operating System(CTOS)

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