Three Dimms; Example Dual Channel Memory Configuration With Four Dimms; Example Dual Channel Memory Configuration With Three Dimms - Intel DZ68BC Product Manual

Installing and Replacing Desktop Board Components
If additional memory is to be used, install another matched pair of DIMMs
(see Figure 16) in the black socket of channel A (DIMM 3) and channel B (DIMM 4).
Figure 16. Example Dual Channel Memory Configuration with Four DIMMs

Three DIMMs

If you want to use three DIMMs in a dual-channel configuration, install a matched pair
of DIMMs equal in speed and size in DIMM 1 and DIMM 3 of channel A. Then install
another DIMM equal to the speed and total size of the DIMMs installed in channel A in
either DIMM 2 or DIMM 4 of channel B (Figure 17).
Figure 17. Example Dual Channel Memory Configuration with Three DIMMs
NOTE
All other memory configurations will result in single channel memory operation.
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