Can't install EFI Firmware Update? Check partition scheme; disconnect peripherals

As we reported earlier, many people (especially MacBook Pro owners) are finding that although, according to the descriptions at Apple's Web site, their computer should be eligible for the recently released EFI firmware updates, nevertheless they get an error message informing them that the update can't be installed, or a flat-out denial from the installer that the machine requires the update.

Now comes word of an amazing possible fix, that has worked for some people (at least three of our readers wrote in independently to say that this was the case for them).

As you may be aware, there are two current "partition schemes" for Macintosh computer disks: the earlier Apple partition scheme, which is used for disks that will boot up a PowerPC machine, and the GUID partition scheme, which is used for disks that will boot up an Intel machine. You could encounter this distinction, for example, when a system installer running one type of machine refuses to let you install the system onto a disk that is partitioned for the other type of machine, as described in this Apple help document and this one.

However, there's an asymmetry here. Although a PPC machine cannot boot up from a GUID-partitioned disk, an Intel machine can boot up from an Apple partition scheme disk. Running an Intel machine, you can't install a system onto an Apple partition scheme disk, but if you start with a disk on which an Intel-appropriate system somehow has been installed, even if it is an Apple partition scheme disk, the Intel machine will start up from it.

This, it seems, is exactly what has happened to our three readers. Each one has written in to say, in effect: "I used Disk Utility to check my partition scheme (as described in this Apple article) and it wasn't GUID-partitioned!" In two cases, this had to do with the fact that the user had installed a new hard drive into the machine, but in one case, the hard drive simply came like that, purchased from the store.

In each case, repartitioning the drive as GUID allowed the firmware update to be installed. But there's a warning involved: repartitioning your drive as GUID will erase all your data! The only way to do this is to back up to some other disk and then restore. This task is not for the faint of heart, although it can be made a lot easier using a utility such as Carbon Copy Cloner or SuperDuper, which can clone your entire hard disk contents from one drive to another.

So the procedure would be: Use Disk Utility to Get Info on your internal drive (the whole thing, not just a partition of it) and thus check the partitioning scheme of your internal drive. If it isn't GUID, then you could clone to an external drive, boot from the external drive or from your installer DVD, repartition the internal drive as GUID, clone back from the external drive to the internal drive, boot up from the internal drive, and perform the firmware update.

Even if you don't perform this entire procedure (which is admittedly more than a little drastic) it would certainly be interesting (and easy) to check whether, if you're having trouble installing the Intel firmware update, your internal drive is using the Apple partition scheme. Please do check, and let us know what you find out.

Also, do note that according to this article from Apple, it might be sufficient to clone or install the system to an external GUID-partitioned disk, boot from that, and install the firmware update, without ever repartitioning the internal disk at all. Firmware lives in your computer's chips, not on the hard disk, so this should work fine.

Peripherals Another idea is simply to make sure no unnecessary peripherals are connected to your computer. Two readers reported independently that merely disconnecting an external firewire drive or USB device allowed them to proceed with the firmware installation. Rebooting in Safe Mode (hold down Shift during the startup procedure) might help too, we're told.

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