Shared switch with RGII and 1Gbps performance

So many routers use a switch to serve the 4 LAN/WAN ports with internal VLAN to split them out, and one or two CPU connected ETH0/ETH1 over RGII

Like this one on the TP-Link C2600, but it is common enough, my C1750 has the same but I could not find such a nice picture.

So I am wondering: If the RGII is also limited to 1Gbps. (as per spec) how is it possible that my router gets a 800Mbps routing performance? I would think there would be a 500Mbps theoretical limit. (tested with iperf3 using software ofloading turned on)

You ever heard of full duplex :wink:.

Doh! It's right there in the RGII specs: "separate eight-bit data paths for receive and transmit,"

Ok, so I need to run 2 iperf3 in anti-parallel.
Not that it is very critical, I do not really need that speed, but just for the heck of it.