Dual channel

If I have two 128 mb modules in dual channel. If I add a third in slot 3, do the two original modules still act in dual channel with only the third as single channel?

 

Adding one more stick of ram will cause all three sticks of the ram to run in single channel mode. Ofcourse, you could always buy two more sticks of 128 and have all 4 sticks run in dual channel!

 

If this is a 4 slotted MOBO.

Some dual channel MOBO's only have three mem slots.
A dual channel MOBO with three slots can sometimes run in dual channel using all three slots But you need equal amount's of mem in each channel.

Another note some MOBO's have problem's running mem in all 4 slots or even reduce the speed from 400 fsb to 333fsb

 

New memory in but not optimal

I just installed an additional 512 mb of RAM to my the 256 mb I had already. During boot up a meesage reported a less than optimal memory configuration and recommended putting the largest modules in slots 1 and 2. I continued anyway and there are no problems--unless you call being able to open numerous windows and not even approach total physical memory a problem! Should I move the 512 module to slot 1? If I do that I will have to move the two current 128 to 3 and 4 to keep them paired.

 

I got a good deal on a single stick of 512 mb. So I'll try foregoing dual chahnnel for more RAM.