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Journeyman III
Journeyman III

Information about AMD Radeon 6970HD GPU

Hi

I have AMD Radeon HD 6970 GPU. It's have 2GB GDDR5 Memory. When i am trying to pass array of 200000000 (i.e 200 million) integer array to OpenCL Kernel it gives me wrong result.

If we count theoretically

200000000 X 4 bye (sizeof integer) = 800000000 bytes

800000000 / 1024 = 781250 KB

781250 / 1024 = 762.939453125 MB

It's less than GDDR 2GB memory

On other side, if i pass upto 64000000 elements array it gives correct result. why this happen?

Can any buddy help me.

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7 Replies
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Grandmaster
Grandmaster

Re: Information about AMD Radeon 6970HD GPU

Hi Buddy!

Are you facing memory allocation errors? or Kernel correctness issues?

Which platform are you in ? (windows ? Linux?)

32 or 64-bit?

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Re: Information about AMD Radeon 6970HD GPU

Did you check to see what the maximum buffer allocation size is for your device?

Jeff

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Journeyman III
Journeyman III

Re: Information about AMD Radeon 6970HD GPU

Hi Himanshu,

Neither facing memory allocation nor Kernel correctness issues. I am facing latency in memory transfer to GPU i am sending approx 8 GB data to GPU it's to much slow as compare to CPU. 

I am using linux platform.

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Journeyman III
Journeyman III

Re: Information about AMD Radeon 6970HD GPU

Hi jeff Golds,

I have check max global memory is approx 2 GB.

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Grandmaster
Grandmaster

Re: Information about AMD Radeon 6970HD GPU

Even if you consider we are utilizing PCIe full bandwidth -- which is 8GB/s -- it will take minimum 1 second to transfer the data to GPU (Assuming pinned memory).

You cannot pin 8GB of memory - The OS will not allow it. So, the runtime will pin them chunk by chunk and start the DMA. So, there will be some latencies preventing us from reaching 8GB/s. It will take more than a second. May be, 1.25 seconds...

What is the time that you are seeing to do the transfer?

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Journeyman III
Journeyman III

Re: Information about AMD Radeon 6970HD GPU

Hi Himanshu,

    My program required approx 2 to 3 sec to transfer data and performing operation on it.

How can I use DMA? Can you give me any sample which transfer data in chunks?

Thanks!!!

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Grandmaster
Grandmaster

Re: Information about AMD Radeon 6970HD GPU

For transferring data and running kernel on 8GB of data, 2-3 seconds may be reasonable. Anyways check http://devgurus.amd.com/message/1296694#1296694

In case you are still not satisfied, please post a small repro case.

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