Ramashiva,
Yes you can use memory interleaving etc even if you Bios does not have a setting. I've done this and gained around 20% with the system being noticably faster.
Take a look at :
http://viahardware.com/memtweakguide1.htm
WPCREDIT and WPCRSET are not very intuitive but with care you can set any features that the chipset supports. Overall I can get up to 40% improvement in memory benchmarks but end up with instability. It takes many weeks to test each option with a solid overnight stability test for each one.
As you sound like a "compulsive tweaker" (as I am) these tools will keep you happy for many months !
It is also a good Idea to donwload the chipset specs from VIA as then you have full details of all parameters you can use.
Good Luck
NB Apologies to anyone anoyed that this thread is not in the correct place.