So today me and my dad upgraded our iMac from 4gb of ram to 16gb of ram, And i want to give minecraft 8gb of ram. I know how to do that, BUT minecraft wont launch after i apply it. My theory is that minecraft still thinks i have only 4gb of ram. Do any of you guys know how to tell minecraft i have 16? All i can think of is to completely reinstall it. 
Holy sweet jesus… there’s barely anything that needs 16gb of RAM to begin with.
I’m not sure about Apple products but for Windows you need a 64-bit operating system to utilise more than 4gb of ram. You also need a 64-bit version of Java to then utilise more than 4gb of ram for Java programs/games.
Keaton! My dad just ordered 16GB of ram for my birthday, glad to know I’m not the only one here! 
Andy is right. With my 8GB it is really hard to go over 3GB of usage, at some point Minecraft can’t use that much RAM because it will only use what it needs. If you run it fine now there is really no reason to adjust it, may just cause more greif than good.
If you know how to set it, then try the 4 gig limit. It may work with just that, but I would do 3 gig myself. My whole system has 2 gigs.
there are cases where minecraft runs soother with just 512mb’s of ramm rather then 1gig, i would say that some trial and errror testing will need to be done to test out how much ramm it really needs… 8gbs for the client may be a bit of overkill XD.
also how did you apply the ramm to minecraft? normally you have to tell java about it like this;
http://www.nextgenupdate.com/forums/mac-discussion/423064-allocate-more-ram-minecraft-mac.html
Oh and while we’re on the topic of performance, have any of you tried Optifine?
http://www.minecraftforum.net/topic/249637-181-optifine-hd-d2-fps-boost-hd-textures/
From what I’ve heard it makes an incredible difference to FPS
kinda wanted to, never took the time to install it though
I can vouch for optifine, as can fatso xD
rather then having just plain fps boosting (which, because of the auto save disabler and the smooth fps feature, it does) you can tweak the rendering of the game to your personal preference, so instead of having just ‘fancy’ and ‘fast’ you can make certain things fancy and other fast depending on what you like, such as have the clouds and trees fancy but have the water, ground and animations on fast. it also allows you to edit that annoying cloud height that passes through the roof of a mountain building and instead make it so the clouds appear at the top of the map or even turn them off completely along with weather (water still has splashing effects) and even the sun and moon. (you can also make it so its allways day or night in game for recording or just to be able to see at night)
WALL OF WORDS!
Yeah i know 8gb is a bit of overkill, And yes minecraft wont launch if i give it more than 4 gigs of ram, ill check out that mod andy, And fatso i did apply the ram to it because it wouldn’t launch. I guess i will be fine, it seems when i dont have minecraft full screen I get 150+ FPS, but when i go full screen i drop down to 60+.
Oh no 60FPS what are you going to do?! XD
Get a PC. Jk 
Correct me if I’m wrong, but the human eye cannot see more than 60fps right? Isn’t that why refresh rates are usually set at 60hrz? Either way, isn’t 60fps really good anyway?
Human eyes can see at around 60fps yea, but you can also watch a film happily at about 30fps.
The lowest fps you can watch without really noticing any flashing or changes is about 25fps, which is what i record in (to save on space and to save my poor little cpu from blowing up XD), anything below 25fps is a no go zone really for a game or such
So yea, 60fps is actually really good =D
24 fps! Sorry, had to be said
Darn it! i have been mistaken… i shall now go hide in the loft =[.
ahh but i did say ‘about’ 25fps 
Yup, generally anything above 30 is considered good and playable and when you hit 24 it starts to become unplayable depending on how fast the game moves.
Ah i accualt do recall watching a Youtube video saying that TONS of fps would actually cause headaches and such :o
so can low fps
Oh no 60FPS what are you going to do?! XD
Get a PC. Jk