I finally got a couple WIZ820io with the W5200 chip. I'm trying to replicate your results on the Due but I'm running into difficulties.
I have it hooked up per the picture I made, hopefully this helps someone else or if I have it hooked up wrong please let me know:
My main problem is that using your modified Ethernet.h and updated w5100.cpp and w5100.h files I'm having a problem with the device locking up if I press the F5 button on my Firefox browser too many times. It seems that if I press the F5 key about once every half a second the Due will crash/lock up and afterwards will not respond to ping or http. Only a reset of the Due through pressing reset button or re-uploading the sketch will allow it to be pinged once again:
Let me know if you have any ideas, I would love to get this thing running reliably. I would hate to be impatient hundreds of miles from home and crash my due/W5200 remotely just because I was hitting refresh on my smartphone too often. Haha!
I'm running the WebServer sketch under:
I have been able to verify that the R3 version of the Arduino Ethernet shield running the W5100 chip does not suffer from this problem. In fact I can hold down the F5 key and it will not drop ping and will continue to respond to http.