Are PC 3200 and PC2700 compatible when you add memory sticks?

Are PC 3200 and PC2700 compatible when you add memory sticks?

 

We have an Optiplex sx270n. It has two sticks of 256 MB DDR - 333 MHz PC 2700.

 

A Dell sales representative says these two sticks can be replaced by a pair of 1 GB DDR DIMM sticks at 400 MHz PC3200. Is this possible?

 

On the other hand, I want to take the two sticks of 256MB and add them to a larger Dell computer, a Dimension 4600, which already has two sticks (128 MB DDR - 400 MHz, PC3200) and four slots. Are the PC3200 sticks compatible with the PC2700 sticks in the same computer? If so, can I use all four slots for these four sticks? Or is it better just to use the two 256MB sticks and replace them where the 128MB sticks were?

 

In hopes of an answer, I am,

 

Arnold Perey, PhD

Aesthetic Realism Foundation Faculty