What Is Flex Mode?
Intel Flex Memory technology dates back to 2004. It lets you use DRAM of different capacities to enable the exploitation of the motherboard’s multi-channel architecture whenever possible. Maybe you already have two 2GB DRAM modules and want to add a 4GB module. Generally, you would be running the 2x 2GB set in dual-channel mode (normally, slots 1/3 or 2/4). With flex mode, you can put the 4GB one in slot 1 and the two 2GB modules in slots 3/4 so that you have 4GB in each channel.
Flex mode can also take into account uneven amounts in the channels — if, say, that 4GB module were 8GB, then you would have 8GB running in dual-channel mode and the leftover 4GB as added capacity in single-channel mode. Another possibility would be to have 8GB in slot one, 2GB in slot two, 4GB in slot three and 4GB in slot four, giving you 18GB total or 16GB in dual-channel mode and 2GB in single-channel mode. This is sort of an odd setup, but I have seen it used. It is more common to have 2 x 8GB and 2 x 4GB where, ideally, it would be placed 8-4-8-4 so that 12GB is in each channel.
While this is a nice feature, I don’t suggest planning to buy DRAM to run in this manner. There are no guarantees that any DRAM you buy will play well with what you already have. We will expand on this in Part 2.