DDR400 Dual channel is slower than single channel?

Here is my setup

Abit AN7
AMD XP 3000+
Kingston DDR400 Dual Channel (2x512mb)

I have had my memory in the non-dual channel slots since i put it together, (I read the manual wrong). I got PC Mark 04 scores of 3600 (max) with o/c, but an average of 3200 w/o o/c. Then I realised yesterday that my memory was not running in dual channel mode, so I swapped slots and now it's activated. I know this because the board now say's 'Dual channel enabled'. But when I run pc mark 04 again, I am getting scored like 2200 or lower. WTF? I've set the ram to run at from 333mhz to 400mhz and it hasnt changed the score any and I dont see any improvment. WTF?

Thanks for any help in this matter. It's reallyt frustrating to see my co workers getting scores of 6000+ with their dual memory setup. Of course they are also running P4's. I would like to see at least 4000 on pc mark.

Welcome to the forums

First of all, dual channel doesnt make as much difference to AMD systems as it does to Intel systems, due to the higher FSBs Intel CPUs have.

I would try running Sandra from www.sisoftware.co.uk - run the memory bandwidth benchmark with dual channel enabled, and with it disabled and see if there is any difference.

Is everything else being kept the same?

Yeah,I got a very slight improvement running dual channel with my NF7-S and a 2500 Barton.Definitely not something I could see a difference in.Only benchmarks,and even then It was barely anything.