memory - Is it bad to use two slots that are not adjacent to each other?

I've heard that you always want the same size of RAM (2x1GB sticks) but does their placement matter? I have four slots on my motherboard but does it matter if the sticks are not adjacent?

This particular question involves the Gateway GM5474

Answer

For dual channel configuration and best performance DIMMs (dual inline memory module) need to be installed in pairs.

look at the pic of dual channel memory slot shown below.

The colors indicate which channel the RAM belong to,channel 0 or channel 1, e.g. lets assume orange is channel 0 and yellow is channel 1(in this picture).Keep in mind that sometimes socket color may also indicates bank as shown in the below picture,G:violet > bank 0 ,orange >bank 1

4 slots in the DIMM suggests that these are divided into 2 banks, and each bank consists of two memory slots.(1 orange slot + 1 yellow slot which are adjacent makes bank 0,PICTURE 1) (violet is bank 0 in PICTURE 2)

Then one can place a matched pair of memory modules in bank 0, but a different-capacity pair of modules in bank 1, as long as they are of the same speed.

Using this scheme, a pair of 2 GB memory modules in bank 0 and a pair of matched 4 GB modules in bank 1 would be acceptable for dual-channel operation.

Modules rated at different speeds can be run in dual-channel mode, although the motherboard will then run all memory modules at the speed of the slowest module.

It is adviced not to put different size and speed of ram into a bank.