If you just bought a new Surface Pro 4 or Surface Book, but find that your
WiFi connection speed is slow, then you might want to check if this solution is something that can fix your problem.

In an answer to a question on Microsoft Answers, a Microsoft Support Engineer has said:
We have a known issue with .41 that results in low throughput with specific access points. The issue is specific to MAC layer aggregation (AMSDU over AMPDU) and only impacts a small subset of access points. We are working on a fix for an upcoming update. Until the fix is available, please update the registry key setting to work around this issue.
The workaround suggested is as follows:
From the WinX Menu, Run regedit to open the Registry Editor:
Navigate to the following key:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\mrvlpcie8897
Look for the key called
TXAMSDU.
Double click or tap on it.
Now
modify its value from 1 to
0.
Exit the Registry Editor and restart your device.
twc