Note:You can type "RAM" in the search box of start menu if you are using Windows Vista and 7 style GUI,or the Magnifier icon for Windows 8,8.1 and 10.http://imgur.com/cu8Dqmz
For Windows XP or older,you can press "Windows + R" to open a window called "Run",type "cmd" and press enter.After an old-style UI window has popped up,type "systeminfo.exe" then enter and you can see the system information as well.http://imgur.com/pHR6aVh
2.If you see keywords like "x86" or "32-bit",you have nothing to do.Please goto step 2.
If I just simply run 1.11.2 with Java 8u111 32bit 128MB-1GB RAM,I probably will have only few fps when initializing the world ,extreme 32 chunks or heavy minigames,and 20-60 fps for stablized small worlds and servers.
Unlike most other games,MC isn't officially supporting Multi-core processors.That means no matter how many cores your CPU has,it still only uses ONE.
Example:AMD FX-8100 @2.8GHz x8 & FX-4170 @4.2GHz x4. 8100 can process at a total speed of 22.4GHz while 4170 is 16.8GHz.
BUT as I said Official Minecraft only uses SINGLE CORE,which means 4170 is actually running 42.8% faster than 8100 when playing MC.
(A little tips:If you want a gaming PC,How many GHz per core is the key.)
Unfortunately,4.2GHz still isn't enough for running MC ,lagless.There is a 3rd-party application named OptiFine,allows Minecraft to run with Dual-Core,doubling the speed of it.4170 can therefore run MC @8.4GHz.
RAM is a zone of your PC where it can store temporarily files for fast access.Giving more RAM to MC will allow it picking data it needs faster,improving FPS.
From SystemInfo,you can know how many RAM your PC has.GIVING TOO MUCH RAM TO MC THAT YOUR PROCESSOR CAN'T RUN THAT FAST WILL MAKE MC BOTTLENECK ->LAG! The official setting is 128MB minimum and 1GB maximum.Most PCs nowadays has 4/8GB ,16GB isn't common,32/64 are rares.For me,I have allocated 2GB minimum and 5GB maximum.When initialising the game it will bottleneck for 1 second,but the rest is smooth as air flow~~
Click "Edit Profile" in launcher.At the bottom ,JVM Arguments,check the box.Manually change -Xmx and -Xmn to what you want.It has to be a number and amount.like 128M for 128MB,1G for 1GB.http://imgur.com/RvIMr9R
Note:MC won't use all of the maximum RAM you have set.
Configure the speed you want by yourself.The higher speed,the more heat will be generated.60-80C is affordable for gaming.You can adjust fan speed too,but it will decreases your fan's lifetime,though just a little bit.