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flat assembler > Projects and Ideas > Programing a Bootstrap

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connor



Joined: 07 Jun 2016
Posts: 51
Location: sj ca
What im thinking about now is mastering the art of making a custom boot program.

To load a file of my choice, in my case a custom cpm86.sys file

and not just that,

to boot in 34/64 bir real mode.


HOW DOES BOOT WORK?


Description: other versions of the cpm system files
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Filename: SYS LOADING PRJ.zip
Filesize: 163.58 KB
Downloaded: 27 Time(s)


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Post 06 Jun 2019, 04:38
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connor



Joined: 07 Jun 2016
Posts: 51
Location: sj ca
putting it in another way;

How do you code a floppy, usb, hard drive or a cd to boot on start up?


a boot disk from scratch?


in 32/64 real mode?

thats supposed to be a question

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Post 12 Jun 2019, 04:49
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 16632
Location: In your JS exploiting you and your system
Normally a boot sector can't do too much, so it simply loads in more sectors from a fixed location on the HDD/SSD to a fixed location in memory and runs that new code. Often the fixed location is just the next sectors after the boot sector. You might find that referred to as a second stage boot loader.

Form there, with more code to do more things it can do much more. So you can have various functions to decode the disk format and find a boot file, switch to 32-bit unreal, or 32-bit protected, or 64-bit protected mode. Or generally whatever is needed. You don't even have to have a disk format in place, or even an OS, your code can be a simple single purpose application.
Post 12 Jun 2019, 06:58
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connor



Joined: 07 Jun 2016
Posts: 51
Location: sj ca
Any exapmles?

& can it all be done with a assembly compiler or do i need something special?
Post 14 Jun 2019, 06:30
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 16632
Location: In your JS exploiting you and your system
There are a few examples of boot sectors on this board. Have a look in the OS Construction forum.

You can do everything with assembler. You don't need anything special.
Post 14 Jun 2019, 06:47
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