Are you using a network switch between the computers? Virtually all computers manufactured in the last eight to ten years have 1000Mbps (Gigabit) network adapters. However, as stated earlier, the computers will only run as fast as the slowest component. So, to run at the fastest speed between the computers, you should have Cat 5e (note the “e” for enhanced) cables and a gigabit network switch. While most newer routers have 100Mbps to 1000Mbps LAN ports, there are still some, including internet service provider gateways, that do run at slower speeds.
The internet provider isn't being used. This is just Puter A and Puter B over a wifi router. Ergo last ditch is a wire direct connect.