Here's the problem:

I want to do a clean install of Mountain Lion on my (custom) Intel 520 SSD inside my iMac. The first time this SSD was setup, it was done by a certified Apple Retailer.

This time, I wanted to use the "Intel SSD Toolbox" to do a "secure erase" of the drive to get it back to full condition. However, to do this, there can be no partition on the drive, and currently the EFI partition is still present.

I searched on AskDifferent and via Google, but it seems removing this partition makes Mountain Lion complain while installing.

So my question is this: (How) can I safely remove the EFI partition so I can use the Intel SSD Toolbox and then install Mountain Lion? I figure the drive initially never came with any EFI partition and the Apple Retailer installed Lion (not Mountain Lion though) just fine, so there has to be a way to tackle this.

I am currently writing, and working on this from Windows 7, my Lion partition is already gone so I can't work from there

1 Answer 1


Delete the EFI partition, do your secure erase, then don't partition or format the drive from Windows 7. Instead, boot from the OSX installer disk or recovery environment, and use its version of Disk Utility to partition the drive, using the GUID partition scheme. Disk Utility will create the EFI partition for you if done this way.

To be clear: the EFI partition doesn't contain any useful data - in fact it's generally completely empty - but it's used by OSX and the Mac's bootloader for installing firmware updates. This is why the installer complains if it doesn't exist.

  • Thank you for the help. Unfortunately, my SSD was "secure erase locked" and according to the Intel tool (and Google) I had to physically unplug it to unlock the drive for a Secure Erase. Not very practical with an iMac so I ended up formatting the drive using Disk Utility and writing 0's to the entire drive. Not sure if it's as efficient as the Intel tool, but it will have to do.
    – j.mertz
    Aug 11, 2012 at 11:18
  • Writing zeroes is actually a bad idea on most SSDs (unless they have special zero-detection), worse than just doing nothing, and can actually degrade performance. If possible in Intel's tool, issue a TRIM command for the whole drive - that should clean it up and reset it back to a fast condition.
    – pmdj
    Aug 11, 2012 at 12:06

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