I previously made a post about swapping the IDE controller from a dead Rev. B motherboard onto a working Rev. A motherboard. After some more thinking I came up with a better solution to my problem, using the Rev. A board to fix the dead Rev. B board.
The dead board would power on but only give four diagnostic beeps. From what I've read this code indicates a bad checksum of the non-boot block area of the Boot ROM. I figured I could reflash the ROM from my working Rev. A board onto my Rev. B board to fix this so I found this post on MacRumors by Joevt to a firmware dumper utility for OSX and proceeded to dump the 1MB ROM from my working board.
The hard part was to desolder the TSOP-40 flash chip from the dead motherboard without damaging anything, with enough flux and my SMD rework station it came off with minimal struggle.
I installed the flash chip into my programmer and dumped the contents. After running the two ROMs in a binary compare program I was was able to confirm that the Rev. B's ROM was modified in its zero space like the diagnostic code said.
After flashing and verifying the good ROM onto the flash chip I reinstalled it onto the Rev. B motherboard and confirmed that there wasn't any solder bridges or loose legs.
Today I was finally able to test if all that work was worth it. I got the motherboard back in its case and went to turn it on and it chimes!
I hope this will help someone else with a New World Mac with a bad Boot ROM that it is possible to repair these boards as long as you have the right equipment.
The dead board would power on but only give four diagnostic beeps. From what I've read this code indicates a bad checksum of the non-boot block area of the Boot ROM. I figured I could reflash the ROM from my working Rev. A board onto my Rev. B board to fix this so I found this post on MacRumors by Joevt to a firmware dumper utility for OSX and proceeded to dump the 1MB ROM from my working board.
The hard part was to desolder the TSOP-40 flash chip from the dead motherboard without damaging anything, with enough flux and my SMD rework station it came off with minimal struggle.
I installed the flash chip into my programmer and dumped the contents. After running the two ROMs in a binary compare program I was was able to confirm that the Rev. B's ROM was modified in its zero space like the diagnostic code said.
After flashing and verifying the good ROM onto the flash chip I reinstalled it onto the Rev. B motherboard and confirmed that there wasn't any solder bridges or loose legs.
Today I was finally able to test if all that work was worth it. I got the motherboard back in its case and went to turn it on and it chimes!
I hope this will help someone else with a New World Mac with a bad Boot ROM that it is possible to repair these boards as long as you have the right equipment.
