[k1w1]

Back in 1999 we built a 100% bit-banged software implementation of 10BASE-T including all of the stack up to UDP & TCP. It was a demonstration project to show off the performance of the 50MHz/50MIPS Scenix microcontroller.

By the time it was commercialized in 2001 the PHY had moved into hardware, but the Ethernet MAC functionality was still software.

https://www.ic72.com/pdf_file/i/428749.pdf

It is funny to see now that we named the chip IP2022 ... IIRC I don't think we were thinking that it was so futuristic it represented what the year 2022 would look like.