Is it possible to install different memory modules in different channels and still profit from dual channel. In channel A I would install 2 samsung ddr2 256mb 533mhz modules and in channel B 2 nanya ddr2 512mb 400 mhz modules.
Yes, it will provide dual channel as long as the 2 sticks in the same channel are matching. But it is always best to match all 4 sticks when populating all 4 slots. If the pairs have different speeds and timings, it can cause problems. But give it a try, it won't hurt anything. Then run CPU-Z to see the results. The faster sticks should default to the slower sticks' speed/timing.