Just like the PlayStation 3 was the launching point for Sony's Blu-ray optical format
for 12-cm disks, the Sony PSP was expected to do the same for the company's proprietary 'Universal Media Disks' format for 6.5 cm disks.
A single layer UMD disk can hold around 900 MB of data, while a dual-layer UMD disk can store approximately 1.8 GB of data.
The UMD did not take off despite it being bundled with the PSP and the format has since been abandoned by Sony on the latest model of the handheld console, the Sony PSP GO.
The lack of copy-protection options on the UMD disks was also seen as one of the major reason that privacy was rampant on the PlayStation Portable.
Storage - For the PlayStation Portable, storage is completely restricted to memory cases. Since it is a Sony device, the company obviously threw in a slot only for its proprietary Memory Stick Duo cards. Users can also use Memory Stick Micro cards with a Duo adaptor.
While older versions of the PSP supported no more than 4 GB cases. The latest version (PSP-3000) along with the latest update claims to be able to support cards of upto 16 GB go size.
While doing away with the UMD drive, the upcoming PSP GO is expected to pack 8-16 GB of onboard flash memory. This is being seen as a sign that Sony is going into online retail distribution for further video game sales on the Sony PSP.