Extra ram slots are often just an extra feature, not a necessity.
Extra ram slots are often just an extra feature, not a necessity.
The 2-slot board is probably set up for dual-channel configuration. The DIMM slots and channels are distinct, and the majority of consumer boards offer two channels.
More RAM lanes provide greater capacity, right? But adding more ports doesn’t automatically increase channels. Take a B450 board as an example. It usually offers four slots, but only dual-channel support. A Ryzen 5 2600 can fit four 8GB modules, giving it 32GB in dual-channel mode. The processor supports dual-channel, and the ports are set up for that configuration. An X399 board behaves differently. A Threadripper 2990WX supports quad-channel, meaning eight 8GB sticks would yield 64GB total. So a B450 with just two slots still offers dual-channel options, while a B450 with four slots also provides dual-channel. (And don’t get me started on budget boards that might have only two slots for cost reasons—different priorities.)
You're mixing up slots and channels. The best number of slots matches the number of channels, but most motherboards double that capacity to support future upgrades without losing existing RAM. On a four-slot board, two slots hold channel A and the other two for channel B. Whether you use one or two DIMMs in each channel keeps it dual-channel.