The playstation monitor uses a thing called frame packing. It's basicly cheating and monitor gets fed 2 frames at the same time within the 24 frames per second rate. (at 1080p) So the monitor is switching between the eyes, when showing 3d, those 2 frames at up to 10x the 24hz rate and getting the eye switching to a seeming 240hz rate. On a movie that tends to make it seem less flickery. On a 720 60hz game the monitor only has to switch a 4x the 60hz rate to get it to 240hz eye switching. Making the game seem even smoother then a movie. hdmi 1.4 is limited to 24hz at 1080p. But sneaking in 2 full 1080p frames is like cheating and gets around that limit.
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The current 3D standards for displays only require 720p at 60hz and 1080p at 24hz. The Playstation 3D display doesn't have any support for 3D formats higher than those two options. Even though HDMI cables have enough bandwidth for 1080p 3D at 60hz, the displays don't support it since 1080p 3D at 60hz isn't a standard yet.
You CAN get 1080p 3D at 60hz, but only from side-by-side 3D, which means the resolution gets cut in half. Arguably this looks worse than full 720p 3D at 60hz though since each eye gets a 960x1080 image instead of a 1280x720 one.
Basically, for games on the Playstation 3D monitor, you're pretty much stuck with 720p.
"Walking tanks must exist somewhere for there to be such attention to detail like this in mech sim." - IGN Steel Battalion review