TechSpot

Memory Size vs Memory Bus

By dragonlord04
Mar 25, 2007
  1. I'm fairly new to comparing video cards, and finding up to date, unbiased articles on this is a pain, so I ask you kind folks this -

    I have a choice of buying 2 similar cards:
    1) GeForce 7600 GS with 512MB video memory and 128-bit memory bus.
    2) ATI Radeon X1900 GT with 256MB video memory and 256-bit memory bus.

    Most other attributes are similar but the ATI is slightly faster speeds (and higher price). Generally speaking though, what is more important: more memory? or better bus?

    Another comparison in a similar price zone is a
    1) GeForce 7600 GS with 512MB video memory and 128-bit memory bus, 533 MHz Memory Clock, 12.8 GB/s Memory Bandwidth. (heat sink-no fan)
    2) GeForce 7600 GT with 256MB video memory, 128-bit memory bus, 1400 MHz Memory Clock, 22.4GB/s Memory Bandwidth. (fan)

    Which of these two would result in better performance? Are fans that noisy?
     
  2. honvetops

    honvetops TS Rookie Posts: 62

    questions first

    What type Operating system are you using ?
    How much memory do you have installed now?
    Is the primary reason for playing games?
    How much money can you spend?
    What type of processor and motherboard do you have?
     
  3. HPCE_Larry

    HPCE_Larry TS Rookie Posts: 189

    a price range would be nice. More important than the memory is the gpu clock speeds. Please provide more information.
     
  4. Grafficks

    Grafficks TS Rookie Posts: 454

    The memory bus is very important when shopping for a graphics card. For the 7600GS you listed, the 512MB of memory is almost useless because the memory interface is only 128-bit. This is the equivalent of trying to obtain water from a large bucket through a tiny pin-hole!

    From the choices you listed, the Radeon X1900 GT would be the ideal selection.

    As for your comparison of the 7600GS vs 7600GT, it is basically quantity vs quality. The 7600GS has more quantity, while the 7600GT has more quality. The 7600GT would be the ideal choice in that comparison, because it has a decent amount of memory with a fast memory clock speed. The 7600GS certainly has more memory, however it is limited to a 128-bit memory bus and has a crippled memory clock speed and bandwidth.

    And finally, no, stock graphics cards fan generally are not too noisy.

    Good luck. :)
     
    1 person likes this.
  5. CMH

    CMH TechSpot Chancellor Posts: 2,573   +9

    are there X1950GTs? I thought they're X1950XT...
     
  6. Grafficks

    Grafficks TS Rookie Posts: 454

    dragonlord04 actually mentioned the x1900GT, not the x1950. :)

    And yes, there is a x1900GT and a x1950GT. I just Google'd them and both these names are existing products.
     
  7. MetalX

    MetalX TechSpot Chancellor Posts: 1,909

    Memory bus and memory speed (which are the deciding factors in the more important memory bandwidth) are much more important than the amount of memory.

    The higher the core clock, shader clock (if applicable) and memory bandwidth (clock is not as important as bandwidth, although it affects bandwidth), the better the GPU will be.

    Memory bandwidth is calculated by multiplying the DDR speed of the memory by the the memory bus divided by eight.

    So you get:
    Where X is memory clock and Y is memory bus:

    X x (Y/8) = memory bandwidth

    So, for a card like the 7600GT with memory clocked at 700MHz (1400MHz DDR) and a 128-bit memory bus:

    1400 x (128/8)
    =1400 x 16
    =22400 MB/s memory bandwidth or 22.4GB/s memory bandwidth

    (Sorry for all the mathematical-ness I wanted to explain properly ;))

    Also, one must take the number of pixel pipelines, vertex shaders and ROPs there are in the GPU, or in the case of 8000 series, the number of unified shaders present in the core, and the clock speed of the unified shaders.


    And I thought I'd add... to answer your last question, here are the video cards you mentioned in order from best to worst:

    X1900GT, 7600GT, 7600GS

    (I've edited this post at least 10 times :))
     
    1 person likes this.
  8. F1N3ST

    F1N3ST TS Rookie Posts: 1,088

    X1950PRO, 1950xt, x1950xtx
     
  9. MetalX

    MetalX TechSpot Chancellor Posts: 1,909

    He didn't mention those, so I didn't include them. And you should say that you listed them worst to best, not best to worst :) Don't want a newbie to come wandering into this thread and take your advice that the PRO is better than the XTX ;)
     
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