@JPKEN,

With limited info you provided it is hard to tell?

First, what is the ISP speed and HOW are you testing.

JPKEN wrote

When connected to Gigabit Ethernet adapter (Model Killer E2400) Download speed is 600 Mbps, Upload speed is SLOW at 2.6 Mbps.

 

However

 

When connected to Gigabit (Model Qualcomm QCA9377 802.11ac Wireless adapter) Download speed is 327.28 Upload speed increases to a normal Upload speed of 53.17 Mbps. 

 

Both adapters were tested on the same computer.

 

All devices tested ok.  

The Killer E2400 is Ethernet, and the Qualcomm is Wireless.

Not unusual for speed variants on the two devices, but usually the Wireless would be lower?

There are MANY reasons why your readings could be correct or bad, and some investigations would be needed and data supplied to pinpoint some areas to look at.

• First off, as I mentioned the ISP Service, can get any faster than that, I'd suspect you have 500Mbps down and 50Mbps up.
• What cable type IS the Ethernet cable, Cat 5, 6, 6e, 7? That can determine max. speed.
• How long is that cable and does it connect directly to the Router or through some switches?
• Have you tried a different cable?
• Have you tried a different Ethernet port on your Router?
• What Negotiation speed for the cable is your Router (Model unspecified) set to? 1GB Fulll?
• How are you testing Speed, via a Browser, Killer S/W, or desktop test program?
• For Wireless, have you run a WiFi Analyzer to see if the Router SSID is on a low usage Channel so as to reduce overload or even tried different Channels to see if the speed can be better?
• For the Wireless, how far is it from the Router? Any walls between it and the router?
• Is QoS set for either adapter OR in the Router?