I recently replaced my USB 3 external 120GB SSD that I had hooked as a Fusion with the 500GB internal HDD. I replaced it with a 500GB SSD that I'm just going to use via the USB 3 enclosure as the boot drive itself without Fusion. My question is however, can I use the internal 500GB drive as a time machine instead of having to hook up another external drive as the time machine? I tried looking this up, but I don't think anyone has ever asked this question. I'm assuming the 5400rpm is the same as the external HD I have hooked up as the time machine.