Can I use more than 4gb memory per slot on a 990 motherboard or am I limited to 16 gb total ?

You will need to check with the motherboard manufacturer if what you are seeking to do is possible.

Hello jerry6,

The memory controller has already been integrated onto processor, but depending on the system manufacturers, the maximum memory support depends on the design of motherboard. So you'd better read the user manual carefully to obtain such information. Most AM3+ processors could support up to 64 GB system memory, so in that case, 32 GB is definitely possible. But you'd better choose the regular DDR3 modules, try the double side 4GB modules with 16 8-bit chips first. Double Side 8GB modules with 16 8-bit chips might be also proper for your system. Anyway, I just wish you good luck!

Best Regards,

Aaron Janagewen