int 13 and el torito floppy boot image - Storage

This is a discussion on int 13 and el torito floppy boot image - Storage ; Hi, I'm hoping someone here has some El Torito experience. I'm using mkisofs to burn a bootable CDROM of the colorForth operating system as if it were a 1.44MB floppy. I could probably get it to work by setting -boot-load-size ...

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Thread: int 13 and el torito floppy boot image

  1. int 13 and el torito floppy boot image

    Hi, I'm hoping someone here has some El Torito experience. I'm using
    mkisofs to burn a bootable CDROM of the colorForth operating system as
    if it were a 1.44MB floppy. I could probably get it to work by setting
    -boot-load-size to the full image, but for various reasons I'd like to
    avoid that, and my reading of the spec doesn't give me any reason to
    believe I'd have to resort to that.

    However, when I attempt to read the first cylinder with this code:

    mov ebx, iobuffer
    mov ax, (2 << 8) + 36 ;# 18 sectors per head, 2 heads
    mov dx, 0x0000 ;# head 0, drive 0
    mov ch, [cylinder + loadaddr]
    mov cl, 1 ;# sector number is 1-based, and we always read from
    first
    int 0x13

    int 13 returns with carry set, and AX=0124 (36 sectors read, and
    "invalid function in AH or invalid parameter". The iobuffer is all
    zeroes after the read.

    I may well be doing something wrong, but meanwhile I'd like to find
    out if anybody has made this work by treating the virtual floppy as a
    real one, and using int 13 to read blocks from the CDROM. Thanks -- jc


  2. Re: int 13 and el torito floppy boot image

    On Apr 27, 10:43 pm, jcomeau_ictx wrote:
    > Hi, I'm hoping someone here has some El Torito experience. I'm using
    > mkisofs to burn a bootable CDROM of the colorForth operating system as
    > if it were a 1.44MB floppy. I could probably get it to work by setting
    > -boot-load-size to the full image, but for various reasons I'd like to
    > avoid that, and my reading of the spec doesn't give me any reason to
    > believe I'd have to resort to that.
    >


    I beginning to think it's not just my programming, especially since it
    boots from a floppy with no problem. I downloaded the win98 boot disk
    from http://freepctech.com/pc/002/files010.shtml, made an ISO image
    using:

    mkisofs -b win98.img -c boot.catalog -o win98.iso README.txt

    Bochs can boot it, as it can my colorForth ISO. VMware cannot boot
    either, which I don't think is a bug in VMware, it usually does just
    what my laptop would do. I guess I could waste another CD and check
    but I'm pretty sure my laptop won't boot win98 from the CDROM either.
    Are there a bunch of buggy El Torito BIOSes out there? Hard to
    believe, this many years after the spec was published.


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