if my cpu usage is at 100%

[shrinkydinx]

that means upgrading my ram wont make encoding any faster, right?

[charleski]

Upgrading your RAM will do nothing unless:
You have too little for your OS, the encoder and its data structures to fit without paging (pretty unlikely if you have 512MB or more).
Your motherboard/memory controller can support RAM with a faster timing than the sticks you have.

[jggimi]

Not neccessarily. Its very dependent upon your individual config. Moving to PC HW/SW forum.

[Shinigami-Sama]

it also depends if your running lots of filters, then adding more memory would mean less paging and slightly higher speeds

[Sirber]

x264 usualy takes me 100-250MB RAM, depending on the source...