# Why the the tool of scissor become slower after I undated my computer?

**URL:** <https://discourse.slicer.org/t/why-the-the-tool-of-scissor-become-slower-after-i-undated-my-computer/10887>\
**Category:** Support\
**Created:** [March 28, 2020, 11:33am UTC](https://discourse.slicer.org/t/why-the-the-tool-of-scissor-become-slower-after-i-undated-my-computer/10887 "2020-03-28T11:33:37Z")\
**Posts on this page:** 1\
**Showing post:** 11

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [April 26, 2021, 1:17pm UTC](https://discourse.slicer.org/t/why-the-the-tool-of-scissor-become-slower-after-i-undated-my-computer/10887/11 "2021-04-26T13:17:35Z")

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Relevant CMake variables and logic is here:

> <https://github.com/Slicer/Slicer/blob/d06e71c8a67c2801ddd78b8f17a663256bae5d7d/CMakeLists.txt#L484..L501>

You can use system TBB or make Slicer download/build TBB as part of the supervuild process. You can find additional logic for this if you search for `Slicer_USE_TBB` in the source code.

In official Slicer releases TBB is probably only used on Windows. @Sam_Horvath can you confirm?

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_[View the full topic](https://discourse.slicer.org/t/why-the-the-tool-of-scissor-become-slower-after-i-undated-my-computer/10887)._