Do RAM DIMM's need to be the same size?

[James Bond]

I know that in the past RAM sticks didn't need to be the same size to function. Has that changed with DDR2 RAM, etc?

Or can I throw different sizes of sticks in virtually any box?

 

[bamacre]

You can use modules with different capacities. It is better to use pairs of modules however, like two 1GB modules, and two 512MB modules for example.

You also will want to install the larger capacity modules in the primary dimm's, read your motherboard manual for how to do this.

Usually, it says to do this...

slot1 - 1GB
slot2 - 512MB
slot3 - 1GB
slot4 - 512MB

But for some boards...

slot1 - 1GB
slot2 - 1GB
slot3 - 512MB
slot4 - 512MB

Again, the motherboard manual will specify.

 

[James Bond]

Okay, now does that logic only apply to dual-channel memory? Or is that a good rule of thumb for all memory?

That being said - is it VITAL that it is configured like this, or just recommended?

 

[bamacre]

Originally posted by: James Bond
Okay, now does that logic only apply to dual-channel memory? Or is that a good rule of thumb for all memory?

There's no physical difference between dual channel memory. Dual channel doesn't describe the memory itself, but the way the memory is being run on the motherboard.

That being said - is it VITAL that it is configured like this, or just recommended?

In most cases, just recommended. But not abiding by the motherboard's manual certainly can cause instability.