According to this brief from VR-Zone, the upcoming release of the G71 graphics chip from nVidia will have 2 flavours, and 2 seperate introduction dates.  Keep your eyes open for more info as it comes.
“There is no doubt NVIDIA will be launching the 90nm G71 in March and the official name will be GeForce 7900. We came to know that there will be 2 versions; the GeForce 7900 GTX 512MB and the GeForce 7900 256MB. The GeForce 7900 GTX will be launched at CeBIT on 9th of March while the GeForce 7900 GT will be launched later on 20th March most likely together with the GeForce 7600 series.”

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