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).