For most motherboard now a days have triple channel, 6 dimm slots (RAM) atleast. But for dual channel it's either you only have 2 slots or 4 slots. You may make combination like 2 x 2gb or 2 x 4gb for two slots. Read your motherboard's manual about how much ram it supports and also depending on what OS you used and how much ram will it support too.
look i have 4 dimm slots but my motherboard is dual channel only, i have read that i can have 2x2 gb in dual chanell mode and the another 1x2gb in single channel mode will it decrease my performance vs triple channel???
Dual channel is not limited to two modules; however, you must install RAM in pairs.
Rules to Enable Dual Channel Mode
To achieve Dual Channel mode, the following conditions must be met:
Matched DIMM configuration in each channel
Same Density (128MB, 256MB, 512MB, etc.)
Matched in both Channel A and Channel B memory channels
Populate symmetrical memory slots (Slot 0 or Slot 1)
Configurations that do not match the above conditions will revert to Single Channel mode.
The following conditions do not need to be met:
Same timing specifications
Same DDR speed
Memory channel speed is determined by the slowest DIMM module populated in the system.
*This really depends on your motherboard. Some manufacturers use a color
-coded system (meaning use the same colors) and some require that you use the symmetrical approach (meaning same slot on both channels).