Need new BIOS image for 820-00165 (seems corrupted, machines runs fine with donor)


Staff member
Yes, I'll try to do it later today.
Dump must be charged on Medusa ROM, and dumpped on 8MB chip soldered on A4064 adapter.
Medusa cannot process the file directly on its ROM yet.
I suggested this to Harald some time ago. He's planning to add this option in the future.

Paul Daniels

Super Moderator
Have I missed something here or is this perhaps a response to the wrong thread?

In the past, I've just flashed a spare chip with the new/fixed image, soldered back on to the board and that was it (using the TL866CS).


Staff member
I was thinking that you need to modify that file.
I also supposed you have Medusa, as you daily repair Macs.
I got confused then...

A BIOS copy from donor board has dirty ME region for any other similar board.
Sometime works without visible issues, sometime not.
After changing serial number, fix checksum is required.

Paul Daniels

Super Moderator
Normally the process I've used is as follows;

1) remove bios from board
2) copy bios to bin image using TL866CS reader (via windows or linux)
3) copy clean ME region file for the board to a new file
4) modify new file with sections of the old bios (ie, starting from the "ssn" string)
5) write newly created bin ( clean ME + old data copied across)
6) solder chip to the mainboard

I'm not doing in-circuit-flashing of these units.


Staff member
Do you only swap generic clean ME into backup BIOS?
Settings of the new (clean) ME region should be configured according with the actual board you work with.

If you have a known good clean ME BIOS, you can just swap Fsys region from the actual board.
This way you build a new clean ME BIOS with the actual SSN of your board.
If you only change SSN into Fsys region, then fix checksum is required.
And Medusa allows to do all these things onboard.


Hi Paul,
Please try the first one, it's your original Bios with ME fixed in case it was corrupted.

The second one is a new clean bios with all your FSYS info transfered into.
Both should work, but i prefere always to try the first one in case there is differences I am not aware of. But never had issues for both.
Let me know if it works, unfortunately I didn?t tested them.

Paul Daniels

Super Moderator
UPDATE: Original + ME fix worked. Didn't get to try the 2nd one, client machine, just happy it's working now (multiple other faults before this one).