Are you running 1.0.10a? If so, there was a huge memory leak that has been fixed in the latest version of ProjectRed. I believe it also exists in 1.0.9. I was running ~20 FPS, until I manually updated all ProjectRed parts. Then, my performance shot up to 60-100 FPS w/o OptiFine and a 64x resource pack.
I don't even have a gaming computer.
There are other factors that affect performance, such as your graphics card, processor, etc.
