Unable to allocate more than 1GB of ram for tekkit

[Thunderr Bane]

So, my friend recently introduced me to minecraft:tekkit, which is really fun. But recently, I've been receiving a lot of lag issues, looking through forums and asking people have led me to the conclusion that I did not have enough RAM

 

Previously, the max amount of RAM I could allocate was 1GB(which was causing lag issues)

But now, after installing java 64 bit, I can allocate up to 14GB(my laptop has 16GB ram, with 14GB available)

 

Problem solved? Apparently not, even though I can allocate up to 14GB, my game will not run unless it's at 1GB. I remembered I found a website where this dude had the same problem as me and managed to solve it by changing some setting somewhere with the code Xmx/Xms 1024(I vaguely remember)

 

If anyone had the same problem and managed to fix it, either by the the way above or another way, please help a fellow minecrafter.

 

Thanks for the help! =D

[Kalbintion]

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