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How important is memory bus width?

i am asking this with reference to this statement that i came across in a forum

"On the 5700 they'll crank it down a notch as we get 128-bit memory, cutting the bandwidth in half from 256-bit. However, since it's gDDR5 memory (quad data rate) it will still offer sufficient bandwidth."

as according to this it dosent have a great amount of effect with ddr5

plz exlain
15 answers Last reply Best Answer
More about important memory width
  1. man you are fast!!!

    i was comparing the specs of 5770 and 6850
    now the 5770 has edge over gpu freq. and memory freq. over 6850
    while 6850 has more stream process. and bus width

    is it something to do with architecture of juniper and barts??

    is performance diff btw these two high as both are mid range cards
  2. good enough for the premium it commands over 5770???
  3. only issue with 6850 is that its a very new product and the models available are all reference boards

    how is msi r6850??
    or do you suggest any other model (except xfx)
  4. will waiting for sometime be good
    maybe the prices come down a bit after the novelty factor dies
    also manufacturers may comeup with custom pcb, designs and coolers
  5. Yeah, theres two methodologies when it comes to memory bandwitdh:
    1: Large data bus, at a lower speed (Lots of data can be read in one memory read, but with longer periods between memory access)
    2: Small(er) data bus, but with a higher speed (less data can be reas in one memory read, but a smaller period exists between read operations).
  6. gamerk316 said:
    Yeah, theres two methodologies when it comes to memory bandwitdh:
    1: Large data bus, at a lower speed (Lots of data can be read in one memory read, but with longer periods between memory access)
    2: Small(er) data bus, but with a higher speed (less data can be reas in one memory read, but a smaller period exists between read operations).



    Which would ultimately be the better choice ?
  7. OS Outlawz said:
    Which would ultimately be the better choice ?


    Large data bus with faster speed !! (best of both worlds)

    In actuality what you need is a balance between the 2 (like everything else in computers) so that the card performs at the best speed it offers and neither of those 2 is bottlenecked by the other ! (ie. a card can only operate at a certain max speed so you need a bus that is sufficient to not be saturated at that speed but you also do not want to pay more for a wider bus that never gets used because the memory speed can not get close to saturating it) -- kind of like the marketing gimmick of adding more ram on a cheap video card to sell more of them (because many consumers think more is better) even though the memory can not be used due to other limitations
  8. Memory really counts for nothing these days. The most common monitor resolution is only 1920x1080, not enough to require that much memory speed or bandwidth.

    Only 2560x1600 displays or eyefinity setups require crazy bandwidth.
  9. do you mean to say that on gddr5 memory type, increasing the bus width from 128 to 256 wont make any big difference (wrt radeon 5700 and 6850)
  10. Best answer
    abu46 said:
    do you mean to say that on gddr5 memory type, increasing the bus width from 128 to 256 wont make any big difference (wrt radeon 5700 and 6850)


    If both have the same amount of DDR5 memory and that memory is running at the same speed then the 256 bit bus would be faster if and only if the 128 bit bus was being fully utilized. -- think of it like a highway full of cars a 12 lane highway only runs faster if the 6 lane highway has all of the lanes full if there are still empty lanes on the 6 lane highway the added cost for 12 lanes is a complete waste - but once you need more than 6 lanes the 12 lanes start to become significant (so if your resolution is high and you have a lot of effects added like high AA, AF etc. so that the 128 bit bus becomes saturated with info then the 256 bit bus will improve things but if using a moderate resolution and\or fewer effects then the performance of the 2 will be about equal (if running the same memory speed)
  11. will it be of significant impact for a res. of 1920x1080??
  12. Not all 6850s are the same

    The Asus and Gigabyte UD-VGA models have the best cooler and overall build quality. Xfx is ok and u get lifetime warranty.

    HIS has the smallest stock cooler.
  13. abu46 said:
    will it be of significant impact for a res. of 1920x1080??


    The 5770 does OK at 1920x1080 as long as your not using a high level of AA and other effects but it does start to show some slow down due to the 128 bit bus at that resolution as you pile on the after effects so if you are looking to buy something for that resolution that can be used with high settings then the 6850 is probably the better way to go (that or the 5850 which has better performance than the 6850 but is about the same price due to the lowering of prices since the release of the 6xxx series.) Like this XFX 5850 for $175 after MIR is a great deal right now.
  14. Best answer selected by abu46.
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