@Mistazet 

Hi,

There can be a few different reasons why the T4U Plus is limited to 270 Mbps, but a more common one is that the Wi-Fi USB adapter might be working in USB 2.0 mode instead of USB 3.0 mode (even if it is plugged into an USB 3.x port).

So, I think you should verify that first. If you don't already have software that can show the currently used mode of attached USB peripheral devices, then you could try "System Information Viewer" from http://rh-software<dot>com (replace <dot> with .)

  @woozle 

It is showing USB 2.1 (2.0) instead of 3.0 - I tried different USB 3.0 ports and still the same

  @Mistazet 

Then you should try a newer driver version.

Either the one from the year 2021 that TP-Link posted here: https://community.tp-link.com/en/home/forum/topic/509006

Or go straight for the newest available 2023 driver that can be downloaded from this third-party website:

https://station-drivers.com/index.php/en-us/component/remository/Drivers/Realtek/Wireless-(Wifi)/RTL8192RU-8188CU-8188CUS-8192CU..../Realtek-RTL8812AU-8192RU-...-Version-1030.44.0822.2023-WHQL/

By the way, even if the newer driver switches the T4U Plus to USB 3.0 SuperSpeed mode, don't expect the wireless speeds to go up substantially. I doubt this dongle can actually outperform an iPhone 13's Wi-Fi.

  @woozle 

I already did it yesterday (driver update) - I will check this card with my laptop tomorrow next to router

  @Mistazet 

Ok there is some problem with this Adapter, I tried to connect to wifi with my laptop (with laptop internal wifi card) and results is 518Mbps, with T4U Plus maximum 300Mbps 

Doesn't matter if it's connected to laptop or my desktop, still max download is 300Mbps

It looks that this Wifi adapter is bad quality or something

  @Mistazet 

When plugged into the laptop, does the T4U Plus switch itself to USB 3 SuperSpeed mode after a connection to the wireless network has been established?

Although USB 2 High Speed mode is rated at "480 Mbps", because of its large protocol overhead the usable data throughput is never more than 300 Mbps.

  @woozle 

still the same USB 2.0 - I tried on 2 laptops and 1 PC. I read that a lot of people have the same issue. TP-Link should fix the drivers or something.

I will return it under warranty because it doesn't work properly.

  @Mistazet 

The drivers are exclusively developed by the designers of the Wi-Fi chips, which is the company Realtek in this case. The best TP-Link could do is to report these issues to Realtek, but given that this series of Wi-Fi chips has been on the market for about 10 years already ...

There used to be AC1200/AC1300 USB Wi-Fi adapters with chips from the company MediaTek, but these haven't been selling for a number of years already, so you would only find them on the second-hand market.