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8GB DDR3 (4GBx2) Ganged or Unganged?

jpnolejpnole Member UncommonPosts: 1,698
in Hardware

Hey all,

Built my first rig in Dec and I've had the two 4GB sticks in slots 2 & 4 since they are the same color (white). 1 & 3 are also the same color (blue) but #1 is obstructed by my aftermarket cooler. My mobo is Gigabyte GA-890FXA-UD5 REV 2.1 as seen here:

 

http://www.overclock.net/amd-motherboards/730776-official-gigabyte-ga-890fxa-ud5-ud7.html

 

All I do is game and surf the net on my PC. It always says my ram is "unganged" at boot. Should I enable "Ganged mode" in my bios or keep it unganged? Are my RAM sticks in the right slots?

 

Thanks!

Comments

  • pawmaulpawmaul Member Posts: 42

    It is amd's version of Nvidia's Locked vs unlocked architecture.



    basically allowing you to use your ram in dual channel vs single channel.



    Ganged = dual channel mode for ram. All cores get access to 100% of the ram.



    unganged = single channel. Each core gets access to a stick of ram.



    In theory, the unganged mode is better as each core will get access to data quicker. In theory.



     

  • jpnolejpnole Member UncommonPosts: 1,698

    So the single channel unganged mode is better than the dual channel ganged mode? I would have guessed dual > single.

  • QuizzicalQuizzical Member LegendaryPosts: 25,355

    You want to use both memory channels, as otherwise, you lose half of your bandwidth.  Consult your motherboard manual to determine which memory slots you should use.

  • jpnolejpnole Member UncommonPosts: 1,698

    Well my mobo runs the ram in dual channel as long as I have them in the same color slots. Both Speccy and CPU-Z show the ram in dual channel mode. From what I am reading on various forums, people mistake ganged/unganged for dual/single channel. Apparently they aren't related. I can easily set my ram to ganged mode in the bios but the bios states that unganged will yield better performance.

  • noquarternoquarter Member Posts: 1,170

    Originally posted by pawmaul
    It is amd's version of Nvidia's Locked vs unlocked architecture.

    basically allowing you to use your ram in dual channel vs single channel.

    Ganged = dual channel mode for ram. All cores get access to 100% of the ram.

    unganged = single channel. Each core gets access to a stick of ram.

    In theory, the unganged mode is better as each core will get access to data quicker. In theory.


    Unganged isn't really correct in that statement. In dual channel the bus is 128 bit (each channel is 64 bits). Unganged is still running in dual channel but the bus is divided back in half in an interleaved fashion creating two 64-bit dual channel buses. This allows 2 smaller operations to be happening at once, so two cores can make demands from the memory at once (or one core can make 2 demands). In ganged it's a single dual-channel 128bit bus, in unganged it's two dual-channel 64bit buses.


    In ganged one core can ask for something from memory at a time and it will get it at 128bit bandwidth.


    In unganged two cores can ask for something at once at get it at 64bit bandwidth each, or one core can ask for two things from memory at once and get them at 64bit bandwidth each (effectively 128bit throughput).


    Soo.. it's almost always better to be running in unganged mode, even though the difference is almost negligible. A single threaded app prefers ganged mode, however it can still get near equal throughput from unganged mode so it won't make a difference. A multi-threaded app (or multitasking) will get better use from unganged because of more efficient memory bus usage.

    tldr; use unganged.

  • jpnolejpnole Member UncommonPosts: 1,698

    Originally posted by noquarter

     



    Originally posted by pawmaul

    It is amd's version of Nvidia's Locked vs unlocked architecture.

     

    basically allowing you to use your ram in dual channel vs single channel.

    Ganged = dual channel mode for ram. All cores get access to 100% of the ram.

    unganged = single channel. Each core gets access to a stick of ram.

    In theory, the unganged mode is better as each core will get access to data quicker. In theory.

     




     

    Unganged isn't really correct in that statement. In dual channel the bus is 128 bit (each channel is 64 bits). Unganged is still running in dual channel but the bus is divided back in half in an interleaved fashion creating two 64-bit dual channel buses. This allows 2 smaller operations to be happening at once, so two cores can make demands from the memory at once (or one core can make 2 demands). In ganged it's a single dual-channel 128bit bus, in unganged it's two dual-channel 64bit buses.



    In ganged one core can ask for something from memory at a time and it will get it at 128bit bandwidth.



    In unganged two cores can ask for something at once at get it at 64bit bandwidth each, or one core can ask for two things from memory at once and get them at 64bit bandwidth each (effectively 128bit throughput).



    Soo.. it's almost always better to be running in unganged mode, even though the difference is almost negligible. A single threaded app prefers ganged mode, however it can still get near equal throughput from unganged mode so it won't make a difference. A multi-threaded app (or multitasking) will get better use from unganged because of more efficient memory bus usage.

     

    tldr; use unganged.

     Awesome response Noquarter - Thanks!

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