my n900 is still slow even though I OCed it with my limits in 250 850

i checked my usage using conky and it revealed that im using 4-7% cpu when offline and 5-25% when online in the internet. Also the ram usage is almost always at 61% and i dont know if that's normal or not.

most of the ram usage comes from the following:
1. Xorg 5.83
2. hildon-desktop 4.49
3. dsme 3.99
4. hildon-status-m 4.65

can anybody explain what are these and why is my ram usage so high? also, some solutions would be greatly appreciated.