Firmware downgrade?

benwiggy · 06-09-2012, 07:15 AM

A general question about firmware updates. I've updated the firmware on a couple of Macs and some other equipment (notably my HP Laserjet). In all cases, it warns that the firmware update cannot be undone and that it is impossible to 'downgrade' firmware once it has been upgraded.

But very often, there are also instructions to re-perform the firmware update if it hasn't successfully been applied.

So if you can fix faulty firmware by reapplying it, why can't you downgrade firmware by applying older firmware data?

DeltaMac · 06-09-2012, 08:58 AM

Apple doesn't provide the older firmware restore software.
An Apple service shop has software that can recover from a failed firmware update.
As you say, Apple has sometimes provided instructions for re-applying the update, but that wouldn't revert to an older firmware version, unless the newer firmware did not get installed at all.
So - outside of an Apple repair depot, you would have to reverse-engineer the firmware on your own - probably a simple task for you, but beyond my knowledge level.

benwiggy · 06-09-2012, 04:03 PM

But, assuming that you do have the data for the previous upgrade, either by having the old firmware update app or by reverse-engineering (which is beyond my time/cost quota, if not also my ability!):
then shouldn't it be possible to apply an older firmware update than is currently installed? Or is there something that checks and prohibits?

This is an entirely hypothetical enquiry. I've just seen the phrase "firmware update cannot be undone" a lot, and if you tell me not to open the box, I want to open the box.

chabig · 06-09-2012, 07:01 PM

Maybe you can, maybe you can't. I'd say it all depends upon the software that's doing the loading. Most don't let you choose the firmware version to install. Some do.

mclbruce · 06-10-2012, 09:09 PM

If HP or Apple (or whoever) issues a series of patches, it could be difficult to go back. The patches might work on different parts of the firmware, and so something newer could still remain even after reapplying an older patch.

On the other hand, if each firmware upgrade completely replaces what came before, then your chances of downgrading successfully would be better.

06-09-2012, 07:15 AM	#1
benwiggy League Commissioner Join Date: Aug 2006 Posts: 5,071	Firmware downgrade? A general question about firmware updates. I've updated the firmware on a couple of Macs and some other equipment (notably my HP Laserjet). In all cases, it warns that the firmware update cannot be undone and that it is impossible to 'downgrade' firmware once it has been upgraded. But very often, there are also instructions to re-perform the firmware update if it hasn't successfully been applied. So if you can fix faulty firmware by reapplying it, why can't you downgrade firmware by applying older firmware data?

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06-09-2012, 08:58 AM	#2
DeltaMac League Commissioner Join Date: Jan 2002 Posts: 7,998	Apple doesn't provide the older firmware restore software. An Apple service shop has software that can recover from a failed firmware update. As you say, Apple has sometimes provided instructions for re-applying the update, but that wouldn't revert to an older firmware version, unless the newer firmware did not get installed at all. So - outside of an Apple repair depot, you would have to reverse-engineer the firmware on your own - probably a simple task for you, but beyond my knowledge level.

06-09-2012, 04:03 PM	#3
benwiggy League Commissioner Join Date: Aug 2006 Posts: 5,071	But, assuming that you do have the data for the previous upgrade, either by having the old firmware update app or by reverse-engineering (which is beyond my time/cost quota, if not also my ability!): then shouldn't it be possible to apply an older firmware update than is currently installed? Or is there something that checks and prohibits? This is an entirely hypothetical enquiry. I've just seen the phrase "firmware update cannot be undone" a lot, and if you tell me not to open the box, I want to open the box.

06-09-2012, 07:01 PM	#4
chabig Hall of Famer Join Date: Jan 2002 Posts: 2,945	Maybe you can, maybe you can't. I'd say it all depends upon the software that's doing the loading. Most don't let you choose the firmware version to install. Some do.

06-10-2012, 09:09 PM	#5
mclbruce Hall of Famer Join Date: Mar 2002 Posts: 3,870	If HP or Apple (or whoever) issues a series of patches, it could be difficult to go back. The patches might work on different parts of the firmware, and so something newer could still remain even after reapplying an older patch. On the other hand, if each firmware upgrade completely replaces what came before, then your chances of downgrading successfully would be better.