Three Dimms; Example Dual Channel Memory Configuration With Four Dimms; Example Dual Channel Memory Configuration With Three Dimms - Intel BOXDP55SB Product Manual

Intel Desktop Board DP55SB Product Guide
Figure 19. 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 0 (blue) and DIMM 1 (black) of channel A.
Install a DIMM equal in speed and total size of the DIMMs installed in channel A in
either DIMM 0 or DIMM 1 of channel B (see Figure 20).
Figure 20. Example Dual Channel Memory Configuration with Three DIMMs
NOTE
All other memory configurations will result in single channel memory operation.
42