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How to calculate memory band width ?

huanshen

How to calculate global memory band width，such as mali-T864 and mali-G52 Mp4?

1、In my past opinion mali-T864 ddr bus width is 64，all core shareing this bus width,ddr frequency is 800MHz, dual channel,so its memory band width is 0.8GHz*64bit/8*2=12.8G/s.It is independent of the core number.But when I read the blog"The Mali GPU: An Abstract Machine, Part 3 - The Midgard Shader Core",it said "The GPU will typically have 32-bits of DDR access (read and write) per core per clock [configurable]",I am very confused,according to this blog,band width is related to the number of cores,each  core can read and write per clock.

2、How to calculate mali-G52 mp4 memory band width?

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  • +1

    There are two separate things here:

    * The GPU ability to request data.
    * The DDR ability to process requests.

    The Mali-G52 MP4 GPU itself will usually have two 128-bit ports on to the internal bus (one for reads, and one for writes). These run at GPU frequency. With a sufficiently high GPU frequency it will be possible for the GPU to read or write data faster than the DDR can process those requests; in these cases the GPU memory interface will start to stall and wait for the DDR to catch up.

    You can measure the amount of bandwidth actually used by the GPU for a specific bit of content by using tools such as Arm Streamline, which can be downloaded as part of Arm Mobile Studio here (for Android devices):

    * https://developer.arm.com/tools-and-software/graphics-and-gaming/arm-mobile-studio

    HTH, 
    Pete

Reply
  • +1

    There are two separate things here:

    * The GPU ability to request data.
    * The DDR ability to process requests.

    The Mali-G52 MP4 GPU itself will usually have two 128-bit ports on to the internal bus (one for reads, and one for writes). These run at GPU frequency. With a sufficiently high GPU frequency it will be possible for the GPU to read or write data faster than the DDR can process those requests; in these cases the GPU memory interface will start to stall and wait for the DDR to catch up.

    You can measure the amount of bandwidth actually used by the GPU for a specific bit of content by using tools such as Arm Streamline, which can be downloaded as part of Arm Mobile Studio here (for Android devices):

    * https://developer.arm.com/tools-and-software/graphics-and-gaming/arm-mobile-studio

    HTH, 
    Pete

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