PowerEdge 800: memory configuration

Hi everybody,

I need your help for a question about memory installation on PowerEdge 800.

The service manual tell me to install only 256-MB, 512-MB, or 1-GB 2-way unbuffered ECC DDR 2 400/533 memory modules. Now, I've installed in the system 4 bank 512mb = 2gb total.

I need to upgrade the server to 4gb. 

The Dell premier page sales me only 1 GB module for Dell PowerEdge 800 - (128 x 72)
- 667 MHz - DDR II SDRAM - ECC - 2R, where 2R means dual rank memory.

The service manual doesn't talk about 1 or 2 rank memory, but only about single or dual channel installation.

The question is: can I install 4 module of this type of memory (1GB - 667 MHz - DDR II SDRAM - ECC - 2R) ?

Thanks to all.