Bulk IN transfer rate issue with FX2LP on Windows

Hi.
I have some problem with transfer rate with asynchronous bulk transfers on
windows.
I wrote a simple test program based on sigrok. It constantly streams data
through bulk endpoint. The firmware for FX2LP is also  based on sigrok.
It works perfectly on linux with transfer rate up to 24MB/s. But on windows
it can work only up to 4 MB/s.
FX2LP have internal FIFO and when it overflow, device stops streaming data,
so it can be latency problem.
I also try to use different USB-controller on PCI card with same result.
Interesting thing is that sigrok Pulseview works fine on windows with
transfer rate up to 24 MB/s.
The code is there: https://github.com/y-salnikov/usb_tst/tree/bulk
Sorry for my english. 



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