Adobe flash CPU Hog when streaming

[tortillasoup]

I've noticed that Adobe Flash on every computer when viewing video online that the CPU utilization is significantly higher when streaming video than when the video is already stored on the computer. For example, on a Pentium III 1ghz (yes that old) youtube fullscreen is unusable as the CPU is being fully tapped out if you play 360p video while the video is being 'streamed' or downloaded to the computer simultaneously. But if you wait for the video to be fully downloaded, the CPU utilization may drop 10% and the video will playback very smoothly. Why is this? I mean I just bought an AMD A10 based laptop and when playing youtube videos at 1080p, if the video isn't fully downloaded, the CPU utilization is 30% with 4 cores but once the video is downloaded, the utilization drops to 10% thanks to the GPU acceleration. This sucks because that means my battery life will suffer since the CPU utilization goes up when ever viewing streamed video sources. I don't remember Windows Media player, Real Player or other such players having this sort of issue. Also, why is HTML5 video playback so extremely CPU intensive? Like I can play 720p video flash on a Pentium M laptop with no gpu acceleration (that I'm aware of) but 360p HTML5 is the max it can handle.