From : Denis Boyles             		Number : 3156   
   To : All                      		 Ref.# : 0      
Subj. : Boot Sector Program      		  Conf : 80xxx
 Date : 07-03-96  Time : 10:23	[1455/1475]

A while ago there was discussion about adding a program to your boot
sector. So for fun I came up with the following debug scripts:

BOOT50.DBG        -The boot patch
SAVEBOOT.DBG      -Save your current boot code to disk for backup.
LOADBOOT.DBG      -Restores the saved boot code.

The program simply call BIOS to change the active character set to an
8x8 matrix giving you 43/50 lines. When you bootup, boing, the switch
will take place and you'll be able to see more on screen when the PC
boots.

You'll need an EGA/VGA BIOS for function to work.

For safety, the program will only patch a boot disk in drive A:, this
allows you play around with out risking your hard drive. If it works ok
on the disk you can try it on your hard drive at your discretion.

So the first thing is to make a bootable floppy disk.

This program asumes A: is your boot drive, but if it isn't just change
the second number in the L & W lines as follows:

        A: = 0
        B: = 1
        C: = 2, etc..


The main program, this patches your boot code by installing the program
into the memory that contains the 'not a boot disk..' messages. It
updates the original JMP to jump to the new code, then it sets up a
stack, calls BIOS and JMPs back to the original starting poit to boot
the computer.

I have tested this on my computer, running MS-DOS 6.22, and it seems to
work fine.


Cut 'N' Save (BOOT50.DBG)
___--------------------------------------------------------------------------
L 0 0 0 1
A 0
JMP 1A0

A 1A0
CLI
XOR AX,AX
MOV SS,AX
MOV SP,FFFF
STI
MOV AX,1112
XOR BL,BL
INT 10
JMP 3E

W 0 0 0 1
Q
___--------------------------------------------------------------------------

To run the program, just type: DEBUG < BOOT50.DBG from DOS and your disk
will be updated. Now try booting and see if it works.

The next two programs are the SAVE / LOAD scripts, make sure you run the
saveboot script first before trying the main program. This makes a
backup copy of your boot code and saves it for later recall.

To run them, just type DEBUG < SAVEBOOT.DBG to make your boot backup or
type DEBUG < LOADBOOT.DBG to restore it.


Cut 'N' Save (SAVEBOOT.DBG)
___--------------------------------------------------------------------------
L 100 0 0 1
N BOOTCODE.BIN
RCX
200
W 100
Q
___--------------------------------------------------------------------------


Cut 'N' Save (LOADBOOT.DBG)
___--------------------------------------------------------------------------
N BOOTCODE.BIN
L 100
W 100 0 0 1
Q
___--------------------------------------------------------------------------

Again when playing around with the boot sector, be careful, the programs
use the disk only, so your hard drive will be safe. You should use a
blank scratch disk rather than a an important one. If you aren't sure
what you are doing then best not to try. You have been WARNED...

Ok enough scaring you, have fun!...

___
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