I've been experimenting with setting up a Windows 8.1 buildbot, and found this ticket after finding a problem with test_threaded_import, testing against the 3.4 branch.

I seem to be have a low syscheckinterval issue similar to that discussed here on some platforms, though I run into it sooner than 0.00001.

If I change the syscheckinterval adjustment to 0.001 the tests run in about 4s.  Just slightly below that, 0.0009, it can take well over an hour when run manually, always getting killed due to a timeout when running the buildbot test batch file.  Each use of check_module_parallel_init in the test takes 20-30 minutes.  During this time the CPU remains pegged at 100%.  

I don't see any additional slow-down between 0.0009 and the default of 0.00001, so it feels more like crossing a threshold somewhere around 1ms than scaling equally around and through that point.

While the machine is not tremendously powerful (it's an Azure VM - single core ~2GHz), everything else is working well and build times and the remainder of the full test suite run in a reasonable time.

-- David