I bought recently W5100 break-out board / module (red, without PoE) I checked most of the examples from the Library "Ethernet" and everything works OK. I plugged it into ArduinoUNO as follows:
CS > UNO pin 10 MOSI > UNO pin 11 MISO > UNO pin 12 SCK > UNO pin 13 RST > +5v VCC > +5v GND > 0V
Then, when I connected to UNO additional module miniSD (connection method below): CS > UNO pin 4 MOSI > UNO pin 11 MISO > UNO pin 12 SCK > UNO pin 13 VCC > +5v GND > 0V
and I have uploaded sketch (originally for EthernetShield with miniSD) web server with support for files with kartySD (Source of https://startingelectronics.org/tutorials/arduino/ethernet-shield-web-server-tutorial/SD-card-web-server/) all but stopped working and in a relatively specific manner. Now, the module W5100 come pings but an attempt to enter the IP address of W5100 browser fails (exceeded the duration of the call) Interestingly, serial console, you can see that in the initial phase of the run index.htm file is seen by ArduinoUNO. from console "SUCCESS - SD card initialized. SUCCESS - Found index.htm file. "
To make sure that the code is all OK, to the same standard EthernetShield ArduinoUNO plugged and the system here works OK (all pings come and the browser is visible web page (index.htm loaded with miniSD)).
My conclusion is that the problem lies somewhere in the SPIbus which, in my case, can not cope with handling two separate modules (miniW5100 + miniSD).
Maybe someone from the forum users had a similar problem? Please help me solve my problem.