[Galaxy S III Q&A, Help & Troubleshooting] gabe1986:
I did it!, I tell you how I did it :)

Hi! I read the full thread, 7 pages!, and (from my point of view), there were no satisfactory question.

Indeed I read your post one month ago, and I started to do some research to do something to improve RAM management in my i9300, I tell you the exact model because I read answers of people with the 2GB model, obviously they don't have this issue.

I did A LOT of things, I tried changing the ROM (at least I used 3 different ROMs), but I just couldn't live without the camera app, and although multitasking was very smooth, from time to time I got a little laggy behavior, and couldn't use some sensors, I had the feeling of an incomplete smartphone. The final issue that made me go back to stock ROM was the extreme over heating that I suspect ended with the life of my SIM card hehe.

I did several tests after installing stock ROM, here I tell you exactly what I did.

1) First, I installed the ROM I9300XXEMB5, a little newer that the one that I had before (I9300XXELLA), it has the freezing fix. This new ROM has several apps that XXELLA didn't. Whe I first ran this ROM I did notice what you told us before, an impresive use of RAM!, more than 600MB used just after a clean install.

2)After having installed this stock ROM I installed a new kernel, Perseus alpha Kernel (http://xdaforums.com/showthread.php?t=1691401), it's good, and for me, now I think it's fundamental :)

3)After having installed Perseus Alpha kernel, I restored to factory defaults

4)After having restored to factory defaults, I looked that RAM usage was still around 600 MB.

5)Then, I went to settings -> applications manager -> ALL, and started to freeze the next apps: AllShare Play, Bubbles, ChatOn, Deep sea, Favorite contacts, Flipboard, Game Hub, Google Play Music, Help, Luminous dots, Music Hub, News Daemon(EUR), Paper Artist, Phase Beam, Photo wall, Polaris Viewer 4.1, S Memo (twice), S Planner, S Suggest, S Voice, Samsung Account, Samsung Backup, Samsung Backup Provider, Samsung Browser SyncAd, Samsung Calendar SyncAd, Samsung Cloud Data Relay, Samsung Contact SyncAda, Samsung Push Service, Samsung SMemo SyncAda, Samsung Syncadapters, Samsung TTS, SNS, Software Update, Stock Daemon, User Manual, Video Hub, Weather Daemon, Weather Widget, Weather Widget Main, Windy weather, Yahoo Finance, Yahoo News.

6)Uff... after having frozen all these apps, I restarted my galaxy, then I checked the RAM status, it was using just 390MB of RAM!!!

7)I installed my personal apps, one by one, and restarting to see if any of these used an unusual amount of RAM, I only noticed that facebook app uses A LOT of RAM, and I decided to search an alternative (Fast for facebook, if you ask), in fact Facebook is not fundamental to me, so I didn't miss native app.

8)At this moment I have the next apps installed: Calculator(stock app), Calendar (google calendar), Camera (stock), Chrome, Clock, Contacts(stock), Downloads, Dropbox(with sync activated), Email(stock), Fast(facebook), Firefox, FM Radio(stock), Gallery(Stock), Gmail, Google, Google Settings, Google+, Group Cast, Hangouts, Internet(Stock browser), Keep, Maps, Messaging, Messenger (Facebook messenger, offical app), Music Player(stock), My Files(stock), Phone(stock), Pie Control, Play Store, Settings(stock), Stweaks(installed with Perseus), Subway Surfers, SuperSU(root), Swiftkey, Swype, Titanium Backup, Translate, Twitter (offical app), Video Player (Stock), Voice Recorder (Stock), Voice Search, Whatsapp, YouTube.

9)Yes, I have installed a lot, but I think that are the apps that I use frequently.

10)After every reboot (that takes aroun 32 seconds), I get around 450 ~ 460 MB of used RAM (around 400MB of free RAM!! :D ), better than 600MB!! witthout any customization.

After all these, I did a little test of multitasking, I opened next apps: Phone, Contacts, Messaging, WhatsApp, Gmail, Firefox and Chrome (and opened wikipedia on both). I got 678 MB of used RAM (the whole RAM is 855MB), and could switch between all of them successfuly :D (apps weren't closed).

Then, I closed all apps with the trash icon, and got 461MB od used RAM!! :D

Now I'm very happy, I don't have that feeling of waste of money anymore ;) , Samsung Galaxy S3 is a powerful device, it's just needed a bit of patience :D

I leave you some screenshots of my screens :), and hope this could help to some people with this multitasking problem :D