Programming BIOS Flash Roms -- Neat trick! 
Author Message
 Programming BIOS Flash Roms -- Neat trick!

        I wanted to make a few minor modifications to the BIOS on my
motherboard, but I realized that if I screwed up badly, my computer
wouldn't boot... So I made a backup ROM using the following procedure
(you can do this on any motherboard that has Flash upgradable bios and
a socketed BIOS EEPROM)
1. Peel off the sticker and check the part number of your BIOS.
2. Purchase an identical or clone of the Flash EEPROM.  Also purchase
a static strap with gator clips on both ends and a high value
resistor.
3. Download the flash bios upgrade utility and an image for it.
4. Study the code of the utility.  Insert a routine that waits for an
external condition just right before it begins writing the image to
ROM (after any "are you sure" interaction. There should be no dos/bios
calls between this wait and the actual writing.  It must be placed
after the CLI instruction. (Interrupts wont work properly when
programming the bios) I used a joybutton input for this.
6. Now boot to a plain dos prompt (either use boot floppy or hold
shift while dos is booting)
7. Run the utility and answer the questions and let it execute to the
point where you are sure it is waiting for the external condition.
8. Open the case of the PC and (making sure you and your chip
ectractor are properly grounded) pop out your BIOS chip.  
9. Connect one end of the gator-clip grounding strap to something
metal on your PC's case and the other to the conductive anti-static
foam the new chip is on.  This should prevent static discharge when
inserting the new chip.
10.  Plug in the new chip.
11.  Trigger the external event (press the joystick button)
12.  After programming the utility should  reboot.  You have just made
a backup of your bios.  Store the other chip in the anti-static foam
and program away knowing full well you have a backup in case you goof
badly.

This procedure worked for me without problems.  However there is
ALWAYS the chance that something could go wrong.  This procedure comes
with absolutely NO warranty, so do so at your own risk.
                                         - Joshua Neal

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Wed, 01 Dec 1999 03:00:00 GMT  
 Programming BIOS Flash Roms -- Neat trick!


Quote:

>    I wanted to make a few minor modifications to the BIOS on my
>motherboard,  << and went a long way to get there >>

Despite all your precautions your trick has a very fundamental flaw:
IC-parts are NEVER specified to be 'hot swappable' (not even those
mounted in a zif-socket).
In semiconductor terms: you're "stressing the part (far!) beyond the
operating area where permanent damage to the device may occur". Or in
layman's terms: if your bios chip survives, it's by luck, not by
prudence.

There is a much safer way:
1) If your bios / motherboard has a recovery procedure: make a backup
of your bios, use the original chip for your experiments. (And check
the maximum number of times the part allows reprogramming)
2) If your bios lacks a recovery facility, look for an inexpensive
external programmer for your bios chip. That allows you to program a
replacement chip and swap them with power removed from your system.
Regards,
Gerard Bok (just remove the asterisks to email)



Sat, 04 Dec 1999 03:00:00 GMT  
 
 [ 2 post ] 

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