MSDOS 2.11 adapted for the Just for Fun v20mbc

** Requires 512KB

IMPORTANT: The files in this repository are under a variety of licenses.

IMPORTANT: No warranty given, no liability accepted if you chose to use this

IMPORTANT: WARNING: Here be bugs aplenty. Don't change or reference other disks...

Want to just run it and not build it? See rdy2run directory

Hardware and firmware:

https://j4f.info/v20-mbc

Set up for building on win32, can build on other platforms Just need an assembler.

Buildable MSDOS source obtained from pcjs

https://www.pcjs.org/blog/2018/11/21/

Derived from MS repo

https://github.com/microsoft/MS-DOS

You will need dosbox-x

https://dosbox-x.com/

Build Loader

Win32 nasm is included. Use a nasm for your platform.

build loader with nasm: nasm loader.asm -fbin

copy loader.asm to autoboot.bin

Customize Bios

Edit skelio.asm to your tastes, primarily to set max memory size -

bios size in paragraphs is used to calculate location of msdos.sys
A paragraph is 16 bytes.
Since loader loads logical sectors, this is the position of msdos in memory
The fat12 format used is 8 sectors/cluster.
msdos will be 512*8 bytes after start of bios
If your bios becomes larger than 4kb, this will be 512*16
You may need to alter the loader to load more sectors **
Bios size - this allows moving msdos.sys to just after the bios to save some bytes of memory. I am currently wasting space
Bios segment - this is where the loader places the bios, my loader uses 00C0

If you change the boot block definition, you will need to alter seltrack to account for a different sectors per track The value is hard coded in the function

Build Image

Run dosbox-x with the build-msdos.cfg
Run dosbox-x with the build-image.cfg
This is not automatic. Input is needed. Watch for errors*
There is a prompt asking for a segment. Enter 00C0 (your bios segment)

Run image

copy autoboot.bin and ds00n00.dsk & ds01n00.dsk to v20mbc Follow directions in rdy2run

Adding software

mount the disk image in dosbox-x: imgmount f ds1n00.dsk -t hdd -fs fat

You can now copy files to the image. Close dosbox-x and recopy to SD.

keyvin / v20mbc-msdos