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Miscellaneous => 16 bit DOS Programming => Topic started by: orock on December 15, 2016, 06:22:04 AM

Title: DVD-RW run on a bare system
Post by: orock on December 15, 2016, 06:22:04 AM
Good day to you !!
Good wishes, respect you impressively.

MASM Forum - this is a wonderful good forum, live chat prompt, nice people, smart smart, friendly atmosphere, very good.

My computer drive, and I want to run Disk DVD-RW independently, program it to start and execute my program out of it.
What would Disk DVD-RW run like operating system, as a closer dos.
As this drive?
When disconnecting the DVD-RW hard drive in the BIOS is defined as the master. Or whatever it is. Main.

In sector 0 compile assembler

What else is needed? Why is not anything happening?
Code: [Select]

        org     0x7C00
                cli                     ;
                mov     ax, cs          ;
                mov     ds, ax
                mov     es, ax
                mov     ss, ax
                mov     sp, 0x7C00      ;
                mov     ax, 0xB800
                mov     gs, ax          ;
                mov     si, msg
                call    k_puts
                hlt                     ;
                jmp     $               ;
                test    al, al
                jz      MiMet1
                mov     ah, 0x0E
                mov     bl, 0x07                ;
                int     0x10
                jmp     k_puts
        msg     db 'Hello world', 0x0d, 0x0a, 0
        times 510-($-$$) db 0
                db 0x55, 0xaa

What else is needed? Why is not anything happening?  :(

DVD-RW in than to open it and see?
How to debug it to produce, how to treat the program, boot sector to do what methods and what programs?

1.) DVD-RW disc is run in the BIOS.
2.) Debugging needed. With XP windose SP3 as a DVD-RW debugging ??
Title: Re: DVD-RW run on a bare system
Post by: hutch-- on December 15, 2016, 10:18:23 AM
Hi, I have had a look at the sample you posted and it is 16 bit code but you need to have more code. For a machine to boot off an external drive, (floppy, CD/DVD, USB drive) you need to have the basic OS files to make it work, in old 16 bit DOS, your bare minimum was the DOS and BIOS system files and COMMAND.COM the system command interpreter.

Now it depends on what you want to do with a machine booted from an external drive, you may be able to find software that will run on a modern OS that will write a DOS style boot sector to an external drive which you can use as a pattern to modify the boot sector into what you want to do.

rufus_bootable_usb with an app called rufus-2.11.exe

I have seen them to make bootable CDs as well but don't have one on my system.

Another alternative is to get a LINUX boot sector from one of the distributions and see if that will do what you require.

Have a look at this web site.

Hmmmm, its a pay for type, sorry about that.
Title: Re: DVD-RW run on a bare system
Post by: mineiro on December 16, 2016, 12:09:01 AM
Hello, you can do tests by using a floppy disk and using a virtual machine.
A floppy to VM is just a file fully filled by zeros, so insert(overwrite) at first byte place (sector 0) of this file with your assembled program and try to boot this file on VM. Use any hexadecimal editor to do this or hexadecimal disk editor.
If you have ms-dos O.S., so, you can change (org 7c00h) to (org 100h) and generate a .com program, this way you don't need reboot every time.
I'm not upgraded with cd/dvd roms but probably have some bios interruptions or port to access these devices like you need do with floppyes and hard drivers, the thing is know how to deal with these grossomodo functions and where these informations (manual, help) are.
If you are trying to create an .iso image, so, you should write .iso with boot sector inside, at sector zero of internal iso image. So, when computer turn on, whats on sector zero will be loaded on memory at address 7c00h using supposed real mode processor. But here I have not updated about these new technologies like UEFI, so real mode cannot be a solution to your case, not sure about this.

search and refine your findings for 'el torito' or 'iso 9660'. Old bios firmware does not allow a bootable cd-rom to be loaded.
Title: Re: DVD-RW run on a bare system
Post by: orock on December 16, 2016, 09:43:45 AM
Thank you very much! Thank you both!