According to the PlayStation 3's included Safety and Support manual, the system will accept any 2.5" Serial ATA hard disc drive, and not only officially licensed Sony products. This opens up the possibility of installing a much larger drive than what the system comes with A Japanese website looked at the performance differences between the 20GB and 60GB PS3 hard drives. The 20GB is a Seagate LD25.1 at 5,400rpm and with with 2MB of cache, while 60 Gig PS3 is a Seagate Momentus 5400.2 running at 5,400rpm with a cache of 8MB. Impress says you should avoid putting in a 7,200 RPM due to the cost and heating concerns, if you're upgrading look at the size and cache level first and foremost.

PS3 IGN