:?: Can i install a 1GB DDR2 stick and a 256MB DDR2 stick together in dual channel mode ?
If i can't, then tell me to install them in the best possible way for the best performance .

In theory you can.

What you need to know is which slots are of which channel. You can't mix different sticks on single channel. Usually, the layout is:
1st slot -1st channel
2nd slot - 2nd channel
3rd slot - 1st channel
4th slot - 2nd channel

After you plug them in correctly, the timings will be set to match slower stick. That is, if the dram settings in BIOS is set on "automatic".

In theory you can.

What you need to know is which slots are of which channel. You can't mix different sticks on single channel. Usually, the layout is:
1st slot -1st channel
2nd slot - 2nd channel
3rd slot - 1st channel
4th slot - 2nd channel
D
After you plug them in correctly, the timings will be set to match slower stick. That is, if the dram settings in BIOS is set on "automatic".

Single channel is where you can mix different sticks, dual channel requires that the modules have the same specs.

The following is from Crucial.

Do I have to buy the same size upgrade as the memory module currently installed in my computer or can I mix different sizes?

In newer systems using SDRAM or DDR SDRAM memory, you can use modules of different densities with no problem. For example, if your computer came with a 128MB memory module, you can add a 256MB module for a total of 384MB of RAM. However, if you have a "dual-channel" system and want to take advantage of that technology, you will need to ensure that the modules in each memory slot are the same density.

You can't mix different sticks on ONE of the channels. They MUST BE IDENTICAL in order to work. I wasn't referring to the single channel motherboards.


Example:

1st channel (Slot A or C) 1 GB stick. Let's say slot A
2nd channel (slot B or D) 256 MB stick

If more RAM is required, and present one is to be kept, only way to expand memory is to get another EXACT stick (brand/model/capacity) and put it on the same channel where the previous one is. So, if the another 1 GB stick is to be used, then the only slot it could be placed in is slot C (appending to the example).

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