Dell PowerEdge M620 Owner's Manual page 201

Three memory channels are allocated to each processor. The number of
channels used and the allowable configurations depend on the memory mode
selected. The channels are organized as follows:
• Channel 0 - sockets 3, 6
• Channel 1 - sockets 2, 5
• Channel 2 - sockets 1, 4
Sockets A1 through A6 are assigned to CPU1; sockets B1 through B6 are
assigned to CPU2.
Advanced ECC Mode Support – PowerEdge M610/M610x
In this configuration, channels 0 and 1 are combined to form one 128-bit
channel. If a memory error occurs on a given chip, the faulty chip is disabled.
Memory modules must be identical in size, speed, and technology in
corresponding slots.
Memory Mirroring Support – PowerEdge M610/M610x
The system supports memory mirroring if identical memory modules are
installed in channel 0 and channel 1 (memory is not installed in channel 2).
Mirroring must also be enabled in the System Setup program. In a mirrored
configuration, the total available system memory is one-half of the total
installed physical memory.
Installing Blade Components
201