like the sgs it is rated at 512, but the fascinate is rated 384 and the tab is also rated as 512. well the tab has 430ish visible and so do we. the sgs all have 302-329 visible. why the confuseion? video ram! people have speculated that the tab doesnt dedicate ram to video so the ram can be used for both, well the ram usage would look higher if that was the case, more would be visable but more would also be in use, not the case with the infuse.
instead it is a game or advertising the total ram vs system. the infuse and the tab must have 512mb system ram and additional video ram. while the sgs has 384mb system ram and 512 total, 128mb being for video. the real questions is do we have all the video ram that the tab does? i heard the tab has 768mb total and that would explain how it can record 1080p video and the infuse cant as that would indicate 256 mb for video or twics as much as the galaxy s. im not sure exactly if the tab really has that much but it needs to support greater resolution with the same processor, maybe they gave it more video ram for that reason and then threw in 1080p recording because they could.
i would say the infuse may have 640mb total, im not sure 768 would be fair to assume. we would see a big boost in 3d performance over the galaxy s's and there would be no reason we couldn't have 1080p recording if that were true.