CES Sony will release the PlayStation Portable firmware that will load the handheld games console with Skype's VoIP app late this month, it said today. But the software will only run on the second-generation PSP.

It's not as yet clear why Sony's is limiting Skype usage to consumers who bought a PSP since September. Apart from being smaller and having a longer battery life, the slim PSP - officially, the PSP-2000 - is supposed to be identical to the original PSP-1000.

That said, the PSP-2000 uses a new remote control connection mechanism, and it's possibly this subtle difference in hardware - and how it's connected up inside the handheld - that may lie at the root of the limit.

Sony also warned that running Skype requires not only a suitable headset - it has one in the works, natch - but also a Memory Stick Duo card installed in the handheld.

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