Step33: Bootblocks

What is a bootblock ?

I worked with floppies disks until very late. Floppy disks are slow and limited in storage. On A500 you can use 880KB on a floppy disk. The disk is divided into sectors, around 80. If I remember well, the directory of a floppy is at sector 40.

When you insert a floppy disk on an Amiga, the first sector is read and executed. It is sector 0. A sector can store 1024 bytes.

You can store nice programs on that space. Viruses also used bootblock to reproduce.

I wrote some bootblocks, so I’m going to explain a bit how it works.

Coding a bootblock

Here is a sample of a BootBlock I’ve created for my utility disk.

It is composed of a copper list for the background color and font color. And one plane with a simple font.

Code source is HERE

Install a bootblock

Once your code is done, you need a program to write it on your disks.

I can not remember which was I was using. I’ll make some research to find it.

On English Amiga Board, I’ve found some info about making the task using Asm One:

WriteSector (WS)

CC (Compute Checksum)

Some cool bootblock demos

Cube-O-Bootic Amiga Bootblock intro by Scarab (1024bytes) 2012

Infect – Wave Bootblock Amiga – Boot Block Amiga
Wave Bootblock by INFECT Commodore Amiga 1024 Bytes of Code (no sound) (c)1992 Marley / Infect

 

Links:

http://wiki.amigaos.net/wiki/Amiga_Floppy_Boot_Process_and_Physical_Layout

http://coppershade.org/articles/More!/Topics/Size_Coding_for_Block_Boot/

http://virus.wikidot.com/bytebandit

PC Tool « Amiga bootblock reader » : http://eab.abime.net/showthread.php?t=64476

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