https://devzone.nordicsemi.com/f/nordic-q-a/62684/the-speed-of-usb-msc-with-softdevice-present-is-very-slowhi support team, i tested the example of \\nRF5_SDK_16\examples\peripheral\usbd_msc , and SD card interface , that with the APP_SDCARD_FREQ_INIT 268435456 (1 M) and APP_SDCARD_FREQ_DATA 2147483648 (8M)in SDK config.h file , this example works fine,en-USTelligent Community 13Thu, 18 Jun 2020 12:48:20 GMThttps://devzone.nordicsemi.com/thread/255772?ContentTypeID=1Thu, 18 Jun 2020 12:48:20 GMT137ad170-7792-4731-bb38-c0d22fbe4515:bd99abec-cd14-4644-a747-5e2d41b2bff4Jared<p>Hi,</p> <p>My guess is that it&#39;s due to Softdevice operations having higher priorities and it&#39;s a matter of scheduling tasks. I think this is acceptable behavior <span class="emoticon" data-url="https://devzone.nordicsemi.com/cfs-file/__key/system/emoji/1f642.svg" title="Slight smile">&#x1f642;</span></p> <p>regards</p> <p>Jared</p><div style="clear:both;"></div>