# memory bandwidth with ECC on

**URL:** <https://forums.developer.nvidia.com/t/memory-bandwidth-with-ecc-on/30533>\
**Category:** CUDA Programming and Performance\
**Created:** [August 22, 2013, 1:09pm UTC](https://forums.developer.nvidia.com/t/memory-bandwidth-with-ecc-on/30533 "2013-08-22T13:09:22Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![woshiwuxin](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@woshiwuxin](https://forums.developer.nvidia.com/u/woshiwuxin)\
**Post date:** [August 22, 2013, 1:09pm UTC](https://forums.developer.nvidia.com/t/memory-bandwidth-with-ecc-on/30533/1 "2013-08-22T13:09:22Z")

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Hi, everyone,

We can easily get the hardware value of the GPU memory bandwidth with ECC off (e.g. 177 Gbytes/sec for Tesla M2090), but how about the memory bandwidth with ECC on? Is it also reduced by 12.5%?

Thank you in advance!

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**Author:** ![njuffa](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@njuffa](https://forums.developer.nvidia.com/u/njuffa)\
**Post date:** [August 23, 2013, 12:23am UTC](https://forums.developer.nvidia.com/t/memory-bandwidth-with-ecc-on/30533/2 "2013-08-23T00:23:48Z")

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Why not simply measure it both ways? For example, on my K20c here I measure the following STREAM bandwidth (standard double-precision variant, i.e. 64-bit accesses):

ECC off 170.5 GB/sec +/-1%  
ECC on 150.0 GB/sec +/-1%

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<div class="post-metadata">

**Author:** ![woshiwuxin](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@woshiwuxin](https://forums.developer.nvidia.com/u/woshiwuxin)\
**Post date:** [August 23, 2013, 8:11am UTC](https://forums.developer.nvidia.com/t/memory-bandwidth-with-ecc-on/30533/3 "2013-08-23T08:11:16Z")

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Thanks!

I was actually asking for “the hardware value of the GPU memory bandwidth”. But anyway, based on your tests, it seems that the ECC may reduce it by 12.5%, which confirms my presumption.

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**Author:** ![njuffa](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@njuffa](https://forums.developer.nvidia.com/u/njuffa)\
**Post date:** [August 23, 2013, 3:22pm UTC](https://forums.developer.nvidia.com/t/memory-bandwidth-with-ecc-on/30533/4 "2013-08-23T15:22:15Z")

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My understanding is the impact of ECC on memory bandwidth depends on the access pattern, so it is not possible to state a single “hardware value”. For a given app, the impact of turning ECC on or off should be easy enough to determine.