I've got MacBookPro9,1 Mid 2012 13" At first I thought that the HDD is bad but I tested it on another PC and the SMART is ok, data can be written and read from file systems on the disk. Also posted this in similar thread, though I have problems with HDD, too.: http://forums.macrumors.com/showthread.php?t=1849439 The funny thing is if I boot Ubuntu from USB flash drive (just copy the contents of ubuntu.iso to a partition on a usb flash drive formated with MBR (haven't tested guid but probably also works) partition table and file system fat32 (vfat in linux) I can partition the ssd disk with GUID partition table, make file systems, write raw data with dd to disk directly or to a filesystem like this (WARNING commands below WILL DESTROY data on your ssd or other drive found as /dev/sda) dd if=/dev/zero of=/dev/sda bs=4096 count=100000 or with a file system: /dev/sda1 is mounted on /mnt/sda1 as hfsplus dd if=/dev/zero of=/mnt/sda1 bs=4096 count=100000 I checked what it had written and the zeroed files are there. Also if I create a partition table (guid) and format the partition w/ hfsplus Yosemite installer sees it but the installation cannot start copying files (the installation stops (but not freezees) on like 20 minutes remaining and thats so for hours) If I put back hdd which stopped booting into Mavericks/Yosemite (not sure which was there previously) I can freely partition or format but Yosemite stops (but not hangs) on some 20 minutes left and stays there forever, logs say that it can't copy the 2nd .pkg file even though the usb installer drive has the .pkg and I even tried a different usb drive- the same. USB installer works with other macs. Mavericks on the other hand proceeds to install and then stops on 1 minute remaining and stays there. Log file is no help. And doesn't boot later.- The grey question mark. I suspect it's the firmware (EFI or SMC) The HDD smart is ok and the ssd is brand new. My firmware/smc: MBP91.00D3.B08 2.2f41 Edit: Figured I can Install Yosemite on external drive and then upgrade SMC firmware from within that working OS. Not sure how to or where to get SMC and FW DOWNgrades though. Will report back tomorrow.