Microsoft Surface Pro 6 Wi-Fi speed problems

Hello community


I have a problem with the built in "marvell avastar" wifi card in my Surface Pro 6.


When I connect to my 2.4Ghz Wi-Fi network the speed I get right next to the accesspoint at best is 144Mbit in "Network Devices -> Wi-Fi - > Status". So the Surface is basically connecting at 2 chains of 20Mhz bandwidth, while the AP is capable of 2 chains of 40Mhz bandwidth which would be 300Mbit. For example my HP laptop easily does that on the same AP where my Surface only does 144Mbit.


So after many hours of research on several forums on the internet such as this one, I manged to make my Surface now show in "Network Devices -> Wi-Fi - > Status" it is connecting at 300Mbit, but unfortunately the AP still only talks to the Surface at 144Mbit. I also confirmed this with real speed tests. And it can't be the AP's fault because it talks at 300Mbit to my HP Laptop.


To achieve this I changed the following registry entry from "ff" to "2"


Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\mrvlpcie8897\ChannelBandwidth


Also I have installed all updates in Windows Update except the May 2020 creators update. And in Device Manager I tried to update the driver for the wifi card, but the newest version is already installed. The driver version is: 15.68.17018.116


Thanks for your help!


Best wishes