DDR2 vs DDR3

By Carlito ยท 7 replies
Aug 13, 2009
  1. Could someone please explain to me the difference between ddr2 and ddr3 ram. I've heard many different explanations and am still confused. My understanding is that the grooves that slot into the mobo (where the brass contacts are) is simply at different positions on the ram modules and the module will only fit into the mobo if it is supported. Am I correct?
  2. Tmagic650

    Tmagic650 TS Ambassador Posts: 17,244   +234

    Yes the DDR2 modules and the DDR3 modules both have 240 pins. The keyways are in different locations so you can only install DDR3 modules in a DDR3 motherboard. DDR's highest speed is 400MHz. DDR2's highest speed is 800MHz. DDR3 highest speed is 1000MHz
  3. klepto12

    klepto12 TechSpot Paladin Posts: 1,115   +9

    um tmagic what do you mean that ddr2 is 800mhz and ddr3 is 1000mhz? um there are ddr2 1066 sticks of ram and ddr3 2000 sticks of ram.
  4. raybay

    raybay TS Evangelist Posts: 7,241   +10

    They do not fit the same slots in the accepted way. They do not work in the same way. They cannot be interchanged...
    It has nothing to do with the frequency, but rather the form.
    You can ruin the memory or the system board, if you force use the wrong memory.
    The different modules are easily to differentiate, so you could not be making a mistake.
    Do you have somebody trying to force the incorrect DDR2 memory into a DDR3 board?
  5. Rick

    Rick TechSpot Staff Posts: 4,572   +65

    Differences between DDR2 and DDR3:
    • Physically different - they are notched differently, although they use the same number of pins and have the same dimensions has DDR2 modules.
    • DDR3 has a lower voltage: 1.5v (DDR3) vs 1.8v (DDR2)
    • DDR3 doubles the buffer size: Basically doubles bandwidth when compared to DDR2 at the same clock speed.
    • DDR3 increases the maximum module size to somewhere above 16GB. The largest DDR2 modules I've seen are 4GB.
  6. Rage_3K_Moiz

    Rage_3K_Moiz Sith Lord Posts: 5,443   +38

    He is correct. The frequency displayed on the chip and advertised as such takes into account the fact that data is transferred on the rising and falling edges of the clock signal, so the actual I/O bus clock for a 400MHz DDR chip is actually 200MHz. However, the maximum I/O clock rate for sticks that are commonly available is limited to 533Mhz (PC2-8500) for DDR2 and 800MHz(PC2-12800) for DDR3.
  7. Carlito

    Carlito TS Member Topic Starter

    Thanks for the input guys. I have actually seen ddr2 1066MHz ram sticks so that means that as Raybay says "It has nothing to do with the frequency, but rather the form". I actually have 2x2gb ddr2 800MHz and could have gone for the higher fequency in ddr2 form, but it would have been redundant as my mobo can only read up to 667MHz. The RAM now just underclocks itself to run at 667MHz and not 800MHz.
  8. 04ihegba

    04ihegba TS Rookie

    Basically you will not be able to run DDR3 on that board. Mobos only support one type of RAM.

    This is because DDR2 and three are completely different internally and thats what allows DDR3 to clock higher. In order to account for these changes, DDR3 mobos have different memory controllers and buses.
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