Updating a Crucial M500 SSD with a usb flash drive on OS X is possible and I show you how:
First download the ISO with the update from the Crucial webpage http://www.crucial.com/usa/en/support-ssd-firmware (you want the “manual boot file” download). Next we need UNetbootin to install all on our flash drive and make it bootable. Grab it over at http://unetbootin.github.io. The rest came with our OS X already (well, beside the flash drive, you need to supply that ;).
The first step is to make sure the stick got a MBR and a FAT32 format. This can easily archived by using the OS X tool diskutil on the command prompt. To do so, open a command prompt, enter “diskutil list” and find your flash drive. There should be a line like “/dev/disk3 (external, physical):” and in the lines below it can (depend if the drive is named) also mention the name. The “/dev/disk3” part is interesting for us, the number behind “disk” can vary depending on your own system. If you wanna make sure not to accidentally kill one of your usb hard drives, unplug them before and only plug the flash drive. Also be sure it say “external, physical”, since the build in drives say “internal, physical” so we can differ between them and we don’t wanna kill the internal hdd(s).
Once we determined the drive number, we can repartition/reformat our flash drive to MBR partition table with one partition and a FAT32 file system format. To do so we punch in at the command prompt “diskutil partitionDisk /dev/disk<number> mbr fat32 FWUPDATE 0b”. I left our here willingly the number to keep you from accidentally killing the wrong drive by just doing blind copy/paste. Please replace “<number>” in the line with the earlier determined number. After the command is done, we have a usb flash drive with a MBR partition table that have one partition named “FWUPDATE” formatted FAT32 which takes all available space. Below you can see how it is supposed to look once you finished with the two commands.
So now we need our UNetbootin. Unpack and launch it, you need administrative privileges to do so as he need to modify the boot sector of your flash drive and can’t do that unless he have admin rights. Once it is started, set it up like in the picture below (select disk image, select the downloaded iso, and make sure the right flash drive is selected by comparing the number to the one determined in the earlier step).
When it is done, he shows a message that this flash drive is prepared but can not be started on a Apple device. You can safely ignore this, I can assure you it does (here a Mac Mini Late 2012 with OS X 10.11 El Capitan at the point of writing this article). It looks like this:
Now we are ready to get updating. Reboot the Mac that have the SSD installed and which needs updating while the flash drive is plugged. To get into the boot selection at the start up you need to press and hold the “alt” or “option” key on the keyboard when the startup chime is playing. The you should get a picture like this after a bit:
There select “Windows”, and he boots from the flash drive. It takes him a little bit, so it might look at first as if he crashed but then it goes on; have patience. Also notice that regardless what OS is installed on that stick, he always call those boot media “Windows”. Once the stick is up, you get a menu with a blue background. There select the 2nd menu entry called “default” with a lower case d. The first is not functioning and thus not of interest to us.
Once that is done, the real upgrade begins. He boot a DOS system, start the upgrade tool, give you a overview if there is a upgradeable ssd detected and ask you to confirm. If the SSD is present and available to upgrade, enter “yes” and press enter. Then he upgrades, and once the “A:\>” prompt appears, power-cycle your Mac to start regular again as we are done (if he didn’t told you there was an error during the flashing).
“Downloading” here means that he download the new software onto the drive, so be not confused by that. I hope this guide was helpful to give you a hint how to upgrade your SSD without taking it out of your mac for the upgrade.
I DON’T TAKE ANY RESPONSIBILITY FOR DAMAGES OR ERRORS/DATALOSS AS A RESULT FROM USING THIS GUIDE. ALWAYS BACKUP BEFORE UPGRADING YOUR FIRMWARE!