I have 2gb ram using 4x 512 sticks, using just two of the sticks I can get 400mhz dual channel DDR but installing all 4 I only get 200mhz and it doesnt say that dual channel is running during post.

Does dual channel only work using 2 sticks or is there a setting somewhere to enable it all ?

Motherboard is av8 3rd eye

Certain models of Athlon 64 get upset if you fill all four memory slots and try and run them at their tightest timings. However you should still be able to run all four sticks in dual channel mode even if you have to reduce the clock speed or timing of the RAM. I have an Athlon 64 PC at work with 4 sticks of memory, runs in dual channel mode fine.

It would suggest that all 4 sticks are not identical.

The mobo *should* automagically detect whether or not it is going to be able to do dual channel. If it is not enabling it, then it would say to me that the mobo doesnt think all of the RAM is compatible.