AnsweredAssumed Answered

Max Read Bandwidth of Trinity APU

Question asked by dertomas on Apr 22, 2013
Latest reply on May 17, 2013 by himanshu.gautam

Hi,

 

I have got a bandwidth question.

 

I got an A10-5800k Trinity APU and I use OpenCL with the integrated GPU Radeon HD 7660D.

Also, I use the Asus F2 A85-M Pro motherboard and 4x 8GB 1866 MHz ram. OS is Windows 7.

 

I used the AMD BufferBandwidth OpenCL example and ran it on my GPU.

There I got about 25 GB/s for reading. All fine.

 

Then I changed the BufferBandwidth code to use not nThreads (some calculated number) but maxThreads (maximal threads for the input data). I also changed the input data from 32 MB to 128 MB.

 

Now I get 70 to 80 GB/s for reading. This sounds somehow too much.

 

My first theoretical calculations  were:

 

1.866 GT/s (Mem freq) * 256 bit (Radeon Memory Bus) * 2 (Dual Channel)  = 111 GB/s

 

There, 70 to 80 GB/s sound plausible. But normal memory only has 64 bit wide buses. With Dual Channel, that would be only 128 bit meaning only 55 GB/s.

 

Can anyone clarify the used buses for me, please? Do you really have 80 GB/s on an integrated CPU or is there a bug in the AMD OpenCL BufferBandwidth test? Are there some resources to do some further reading?

 

Thanks a lot!

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