in DDR dual channel boards (SDRAM cann't do dual channel, and RDRAM has to be in pairs no matter what)
you can have 1, which is single channel, and 3 which is single channel
so if you had 3 sticks, it'd be single channel, but more RAM
depends on what you need, capacity, or bandwidth
2 or 4 sticks (or any other number divisible by 2)
would provide dual channel
but each DIMM (to run dual channel) has to have a matched stick
2x512 and 2x128 is possible
but 2x512 1x256 and 1x128 would yield all single channel
it also all has to run the same speed
is it true u have to install memory in pairs in dual channel motherboards except if ure using only 1 stick?
for example if ur mobo has 4 dimm slots and u have 2 occupied, can u put in an additional stick to have 3 sticks? or do u have to put in pairs so u can have only 1,2, or 4 combinations?