TechSpot

Lost in "BandWidth"

By Raiders
Mar 24, 2004
  1. Please all bare with me,,
    After reading several threads and posts something is really twisting my brain,,Bandwidth?

    Ok if the standard/average "Bandwidth" of an 8X AGP card is around 6GB/S and the "Bandwidth" of the standard 8X AGP slot is 2.2GB/s,,isn't that a major Bottleneck in the performanc of the card itself?
    Correct me if im wrong,, But the "Bandwidth" of the AGP card is between the VGA mem and the GPU, and the "Bandwidth " of the Slot itself is between the Slot & CPU,, That equals a major bottleneck rite? What does the card GPU do with the "Bandwidth" Difference??
     
  2. Rick

    Rick TechSpot Staff Posts: 6,305   +52 Staff Member

    Well, it works differently than you are guessing. Good observation though.

    Most of the work is done on the grahpics card itself (graphics memory & GPU). Once the graphics card does most of the work, it sends the remaining data across the AGP bus to the CPU.

    The amount of data that traverses the AGP bus is FAR less than the actual data that is manipulated by the graphics card locally.
     
  3. Raiders

    Raiders TS Rookie Topic Starter Posts: 118

    Cool, That helps a bit Rick,,Thanks
     
  4. Raiders

    Raiders TS Rookie Topic Starter Posts: 118

    Hi All,
    I have another Question for ya,,i have done some research on overclocking,,i understand that as the FSB goes up so doesnt the pci/agp bus. are thare any "adverce" effects on the respective cards in doing so? I have 2 pci cards, a 1394 pci card and a 5.1 surround sound card.

    I'm looking more into it but im not reading on any thing about it.
    also i cant "Lock" my AGP/PCI bus.

    thanks again
     
  5. vassil3427

    vassil3427 TS Rookie Posts: 822

    Yes there are adverse affects if you push things too far, you can kill Hard Drives, and any PCI card by overclocking the FSB if you cant lock the AGP/PCi bus...
     
  6. Raiders

    Raiders TS Rookie Topic Starter Posts: 118

    I thank y'all for the wizdom,i dont mean to beat a dead horse so ill keep it short. I wont know i went too far,, till i go too far huh? LOL

    I'm learning LOL
    Thanks all
     
  7. Steg

    Steg TS Rookie Posts: 422

    Just to clarify - the insane amounts of bandwidth that graphics cards push today (20+gb/s) is not bottlenecked in anyway by the AGP bus. The AGP bus just transmits data to the graphics card in the form of models/textures/shaders etc. Whill the graphics card bandwidth is used for moving data about for texture filtering/Anti-Aliasing/shader calculations/lighting etc - the data for which is generated on the graphics card - not transfered over the AGP bus - so in short - the higher the memory bandwidth the better dispite the fact that the AGP bandwidth is limited to 2.2Gb/s

    Steg
     
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