As far as the actual manual and a forum post or two in the Dell forums where a Dell engineer helped somebody with memory configuration questions it only supports 16GB DIMMs.Are you sure they won't take 32gb modules? I think my r410 can so I'd be surprised if your 510 can't.
Well I would do 8x for $450 shipped if you want to tryAs far as the actual manual and a forum post or two in the Dell forums where a Dell engineer helped somebody with memory configuration questions it only supports 16GB DIMMs.
However I would not be entirely surprised that it does support 32GB and simply 32GB did not exist at the time that the documentation was created as the R410 manual also only states 16GB DIMMs as the largest.
So that makes me wonder if the R510 will support 256GB of RAM or still max at 128GB using the larger DIMMs. The quad rank stuff will undoubtedly slow down the memory speed but for my use that wont be a big deal.