Info coming from several sources suggests that Nvidia decided to accelerate the launch of its most powerful G90 graphics chips in order to battle AMD's upcoming Radeon HD 4800.
Leaked info and underground rumors have it that GeForce 9900 GTX and GeForce 9900 GTS might hit retail as soon as July. AMD's Radeon HD 4800 is expected to be launched in May, though.
There is no solid info about both 9900 cards' specs, but Nvidia has already said that the architecture behind the flagship will be "extraordinarily complex" with as many as one billion transistors on the GTX. GeForce 9900 GTX is expected to host 1GB video memory with 512 bit interface, while the GeForce 9900 GTS is expected to have 640 or 768 MB video memory with 448 bit interface; but then again, those are not confirmed yet.