Re: Custom bootloader?

On Jan 19, 7:25 am, lyricalnanoha
<lyricalnan...@xxxxxxxxxxxxxxxxxxxxx> wrote:
I've been thinking about this and I'm getting closer to being ACTUALLY
able to do this.

What I want to do is take a file which loads at $2000, make its type S
(and its format raw and headerless, unlike DOS 3.3's B type), and have the
bootstrap search for it (a la ProDOS but with a DOS 3.3 filesystem).  I
can presently read files from a DOS 3.3 filesystem but only with a disk
image and in C.

p-code -

search dir for file: "DOS LOADER"
   not found: display error message "CANNOT FIND DOS LOADER" / hang
   found: check filetype
     not S: display error message "CANNOT EXECUTE DOS LOADER" / hang
     S: attempt to read it starting at $2000
        cannot read: display error "CANNOT READ DOS LOADER" / hang
        shut off the motor and JMP $2000

(Obviously RWTS is out of the question but I could perhaps place a
mini-RWTS somewhere?)

I could build on this further and make the menu I've been planning.

-uso.

If you want DOS 3.3 to work, then you'll have to make it an executable
program and use something like copy ][ plus to set it as the "hello"
program. (not sure about S type -- but B and A work). The less you
need from Dos 3.3, the closer to boot-time you can get your program to
load. In the boot sector, there are a list of sectors to be pre-
loaded for Boot 1. After Boot 1, additional tracks and sectors are
loaded. You could, for example, modify this list so that your program
is loaded during this sequence and modify the dos cold start to jump
to your program when it is finished.

I guess it depends on how crazy you want to get. ;-)

-B
.

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