What exactly is the difference between these standard in RAM memory: DDR (DDR1), DD2, and DD3? Can a computer accept combination of these or all memories have to be the same?
The newest standard for memory is DDR3, then DDR2, and so on. The memory standards are increasing in speed, stability. You cannot mix the different standards in the same pc, if you do, you will 'confuse' the computer and it will usually not even boot up. If you go to the manufacturers website for your motherboard and type in the model number it will show you which kind your board will support.
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