Mix Single and Dual Rank DIMM's

Hi

I upgraded RAM from 12GB (6x2GB single rank) to 64GB (8x8GB dual rank) on a R710. I putted the new dual rank DIMM's in on optimizer mode as per the user manual.

I'm wondering if I can use the single rank DIMM's also? Is there any config where I can use both?

I have latest BIOS, ESM, Lifecycle controller etc..

Thanks