Service Forum

[steve5214]

Victor,
I have a similar project to the last one....although this was caused by the A20m being flashed with A20p bios...I wouldnt have thought it would cause too much of a problem but the laptop is or seems dead...can I use the r24rf08 to read the whole BIOS segment.
Cheers
Steve.

[victor]

Steve,

The eeprom 24RF08 doesn't contain the BIOS executable code. It has only some info used by the BIOS.
If you flashed the BIOS (which is using other chip) with a wrong image then you have 2 choices left:

-if the BIOS bootblock is still intact then you can flash from a floppy disk. Boot block is a special zone of BIOS that is write protected and his role is to upload and execute the main routines. Also it can be used to recover the BIOS if everything went bad.

-flash using a programmer and a good BIOS image.

I don't know exactly how reacts the BIOS boot block on A20 because I have never been in the situation to flash using it, but usually when you power up the laptop a message should appear on screen asking an image disk. If not, you should see the floppy drive spinning and trying to read the disk.

[steve5214]

Victor,
Ok..I understand...I would need to reprogram the 28f004b5 ? have you eber done this yourself ?.... just had a quick look around and the Embest Flash Programmer looks like it would do it... but what would you recomend ?
Cheers
Steve.

[bob]

Steve, anything that can write that chip will be the best.
I suggest you to clear the prom first including the boot block, then flash a good BIOS code.
That should do it.

Good luck, mate

[steve5214]

Bob
I have finally got around to putting the A20 back together and it does try to read from the floppy..but I'm unsure what to put onto the floppy for it to read.
Cheers
Steve.

[victor]

Goto IBM support and get the latest BIOS update.
Make a bootable floppy, copy the BIOS update there and try to boot the laptop with it. The BIOS bootblock will search for a bootable floppy and/or a valid BIOS image.

If the laptop boots up, simply run the utility and write the BIOS. In some cases Bios bootstrap it self will search for a .bin, no need to run a utility.

That would be all, you'll see how it turns out.

Good luck!

[steve5214]

Hi Victor,
Nice to hear from you again.
Wont boot so far....
Goto IBM support and get the latest BIOS update.- have done that
Make a bootable floppy- from the downloaded IBM bios or just a bootable blank floppy ?
copy the BIOS update there - If I am copying to a blank bootable floppy which files do I copy to it ? FL1/2/3 or all ?
and try to boot the laptop with it.
The BIOS bootblock will search for a bootable floppy and/or a valid BIOS image. If the bootblock is searching for a valid bios what extension (.BIN ?) will it look for ?

Cheers
Steve.

[victor]

http://www-307.ibm.com/pc/support/site.wss/document.do?sitestyle=ibm&lndocid=MIGR-4JWNTQ

Download the utility and create the BIOS update diskette.
When power on, the a20m should try to run the autoexec.bat and start the utility. This is what almost all boot blocks should do.

[steve5214]

Victor,

Already tried that, as I say it seems to read the disk but then nothing.
What is block #7 used for in the eeprom ?

Cheers
Steve.

[victor]

I wonder what if you try with a Hardware maintenance disk. Just to see if it boots.

The second option is to copy the content with a programmer. Willem is pretty good.
So, you need a hot air station to dissolder the chip, program the BIOS binary and solder back. Easy