Based on the naming, I had assumed that FIDO1100, FIDO2100, FIDO5100 and FIDO5200 are fundamentally the same. But I notices that the FIDO1100 in the datasheet is advertised as a "regular" MCU which can be C programmed over JTAG. While the other 3 chips seems to be actual special purpose microcontrollers which acts as a ethernet switch.
What I try to understand, what are the differences between the 5x00 family and the 2100? Newer, more protocols more efficient? And is it correct that the FIDO1100 does not act as an ethernet switch, rather was designed as a 'perfect' host controller for the FIDO2100?