Rumour has it that NVIDIA is going to launch another GPU with a weird amount of RAM memory:
Fudzilla says Nvidia has two next-generation graphics cards up its sleeve. One is code-named D10U-30 and will feature 1024MB of GDDR3 memory, while the other is code-named D10U-20 and will supposedly come with 896MB of GDDR3 RAM. If accurate, this information suggests Nvidia could differentiate the two models by playing with the width of the memory bus. Fudzilla doesn't quote any numbers there, but the D10U-30 could have a 512-bit bus, while the D10U-20 could conceivably feature a tighter 448-bit bus.
We may find out for sure soon. The rumor mill suggests Nvidia's next-gen cards are due out in the third quarter of this year, possibly as early as July.