Dell R710 - Memory Configuration

Hi All,

I'm sure I'm missing something but I've read the two technical documents regarding memory configuration in the Dell R710.

I've got a server that currently has 48GB in laid out as follows

A1 - 4GB

A4 - 4GB

A2 - 4GB

A5 - 4GB

A3 - 4GB

A6 - 4GB

(This is then the same on the B side)

According to the BIOS it's set to 'Optimized'

Now I have 2x16GB Sticks which I wanted to install, the only way I could get it working without the BIOS moaning was to install as follows:

A2 - 16GB

A5 - 4GB

A8 - 4GB

(Duplicated on B side)

Giving 72GB.

As I read the manual I should be able to mix memory sizes for 'optimized' as long as I go from A1 to A9 and so I have a further 6x4GB sticks left I want to install.

My logic is I can fill from A1 to A9, mixing the 16GB in, however when I try I get the error about A1/A2/A3 needing to be the same?

Am I missing something simple? I'm unable to make changes in the BIOS, the memory is all the same type (Purchased from Dell)