Hp dv6 with 4 gb ram, so I don't think there's any problem. I had been using lm 12 kde, and everything was smooth but it got or gonna get obsolete in near future.
I use HDMI cable too often to watch movies/youtubes etc. on TV. However, after my initial post, I tried to check what's really causing the problem, and it is because of my fav. online game. I play the game with 1024 x 768 resolution on my 1366 x 768 resolution laptop.
Every time, I play the game, I change the resolution setting of the laptop to match that of the game... but I occasionally face graphics and other problems in doing so and if I don't change the resolution setting of the laptop, it also gives me problems ...... e.g. I get distorted graphics, fan whizzing, laptop responding slowly etc. I dont wanna change the resolutino setting of the game, as I am comfortable with that setting and I know that that shouldn't be a problem as kde and gnome were quite ok with it. In fact, HDMI dual monitor was also possible with kde and gnome, but not with this cinnamon.
To cut the story short, I suspect this is to do with cinnamon.