Most formatting utilities (not including quick format) do a zero-fill on the drive. SSDs actually need to be "one-filled" in order to be erased by software. By zero-filling an SSD, you basically cause massive slowdown until the controller erases all of the blocks that are now filled with zeroes. The best thing to do is use Secure Erase (or Sanitary_erase for OCZ drives if you want) as this essentially resets the volume bitmap maintained by the controller, telling it that all blocks are invalid and can be pre-erased. The advantage is that only the blocks containing zeroes will need to be erased, instead of every block. Check the SSD sticky in this forum for the first Anandtech article, it has a page on Secure Erase.