# Usage of Unified Memory on R28.1 vs R24.2.1

**URL:** <https://forums.developer.nvidia.com/t/usage-of-unified-memory-on-r28-1-vs-r24-2-1/59874>\
**Category:** Jetson TX2\
**Created:** [April 5, 2018, 1:57pm UTC](https://forums.developer.nvidia.com/t/usage-of-unified-memory-on-r28-1-vs-r24-2-1/59874 "2018-04-05T13:57:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![lamegeorge](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@lamegeorge](https://forums.developer.nvidia.com/u/lamegeorge)\
**Post date:** [April 5, 2018, 1:57pm UTC](https://forums.developer.nvidia.com/t/usage-of-unified-memory-on-r28-1-vs-r24-2-1/59874/1 "2018-04-05T13:57:06Z")

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Hi Guys,

I have built a CUDA-based application which uses Unified Memory to write the output of a kernel. Once the output is written I try to access the same on CPU.

When I try to achieve the above task by using cudaMallocManaged, it works well on R24.2.1 ( TX1 platform) but seems to give “Bus Error” on R28.1 ( TX2 platform) and the pointer says “Cannot be accessed” right after the kernel call.

Kindly let me know where I could be making a mistake. Please help me out.

Thanks.

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**Author:** ![AastaLLL](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/aastalll/32/14043_2.png) [@AastaLLL](https://forums.developer.nvidia.com/u/AastaLLL)\
**Post date:** [April 9, 2018, 8:30am UTC](https://forums.developer.nvidia.com/t/usage-of-unified-memory-on-r28-1-vs-r24-2-1/59874/2 "2018-04-09T08:30:08Z")

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Hi,

Usually, Bus Error occurs when CPU/GPU concurrent accesses an unified memory  
Please remember to call _cudaDeviceSynchronize()_ before accessing with CPU.

If this issue goes on, could you provide an example with us to reproduce?  
Thanks.

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**Author:** ![nadeemm](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/nadeemm/32/367020_2.png) [@nadeemm](https://forums.developer.nvidia.com/u/nadeemm)\
**Post date:** [October 18, 2021, 6:28pm UTC](https://forums.developer.nvidia.com/t/usage-of-unified-memory-on-r28-1-vs-r24-2-1/59874/3 "2021-10-18T18:28:40Z")

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