if you go to the launch.bat and edit it, you can change how much ram it uses. tekkit servers are automatically set to use up to 5GB ram so if you want to change this you can. to change this just set -Xmx3G to -Xmx512M and set the -Xmx2G to -Xmx512M as well. this will tell it to run at a maximum of 1024MB RAM. the performance may go down but the RAM usage will go down. hope this helps.