NothingIsTrue,
My question is directed to Americasteam because he is informing me that "available ram" has nothing to do with the hiccups of S4. I am sorry for the confusion. Maybe lag is considered as hiccups. I believed when a program lagged, usually compatibility of Softwares, Hardware, and lack of free RAM. Uninstall the programs that didn't work, and kept those function with S4.
I used Samsung's S2, Note, S3, S3 LTE(2GB RAM), Note2, and now S4. I love Samsung's improvements on their mobile phone each time because I have to switch languages(Asia) when answering emails and messages. Note 2 was the best suited for my purposes and enjoyed the most.
When the S4 arrives, I immediately reserved one and I decided to use S4 3G version(4+4) because according to many review that it is better suited for gaming. I don't root my mobile phone, I played an old simulation game from Kairosoft "Grand Prix Story". I started having lag in the game(standalone), this never happens to me with S3 LTE and Note 2.
So I checked the RAM Manager to see what is going on. According to the RAM, S4 used 1.5GB/1.8GB. I just press the clear memory button to free up the memory. I was shocked to see that it used up 1.2GB of RAM when clear memory, so I disabled all the new functions from S4(now 1.12GB/1.82GB). If I remembered correctly, S3LTE(Asia) used around 680MB/1.82GB and Note2 is around 850MB/1.82GB when clear memory.
I restarted the game, there slight improved but lag happens every now and then which I can live with. "Grand Prix Story" is a game that simulated managing a racing team. I don't think this game took up a lot of result because I played on older phones without any problems.
I turned off many new options except wifi and bluetooth, I will clear memory at RAM Manager whenever I finished using an app. This annoys me because the Samsung's wigets or Jellybean are eating up my free/available RAM and I cannot stop them from doing(I don't know will rooting help). I updated the firmware twice(as usual new phone will have glitches), I thought this will solve the problem because after updated the firmware at the beginning the total RAM used is around 800MB/1.82GB. I thought that solved the problem but a hour later the system go back and used 1.18GB/1.82GB.
Right Now, I felt that the S4 is like the Older Sony Xperia Series with 1GB RAM but with better camera and screen quality. The lower spec phone, Sony's widget and Android used about 680MB/1GB. Xperia Z improved a lot (2GB RAM) but somehow it is not as user friendly as Samsung's Android phone. Sony still has a long road ahead.
Maybe Americasteam is correct, it is the software optimization between the new widgets from Samsung. S3 LTE and Note 2 are the best Samsung Phone, everything smooth and fast. S4 looks good but the performance is not up to my expectation.
Samsung is behaving like old Hong Kong Land Developers, the big difference between the constucted area vs. the actual usable area.....(Constructed Area 550SQ. FT./Actual Usable area 350SQ. FT.) We paid for the constructed area until recently the regulation changed to actual usable area. S4 has 2GB of RAM/16GB Storage in specification/ Actual Usable 690MB/ 8.92GB. It is funny to me....
Typically, 2GB RAM is more than enough if the system left with 1GB usable RAM remaining. S4 with all these new functions, 2GB just not enough.