"High-Speed Serial I/O Made Simple: A Designers’ Guide, with FPGA Applications" (2005):

https://www.xilinx.com/publications/archives/books/serialio....

It's an under-told tale that open CPU's are "easy" to make, but if you actually want to actually run that chip it's everything else that makes it inordinately hard.

Probably like 99.9% of devices with USB hosts all use the same 4-5 different design families of host controllers. A huge number of sound chips are Cadence/Tensilica's HiFi 4/5 chip. Dram controllers, PCIe blocks... There's so many modular blocks used in making chips, where a pre-qualified design that already has been validated on a variety of fabs is just how everyone does it.

This is a 5 year old, barely updated project. There's no clear data on what was achieved that I can see here. But just getting a start doing chip design that interfaces with the world beyond the chip is a huge huge step forward. Building, characterizing what we get, tweaking & trying over again is what it's gonna take to make open source chips emerge & be able to stand on their own.

The devil really is in the details with things like this. 1 in 10 million events which may be hard to trigger in a detailed analogue simulation can occur many times per second when you run it in silicon and make it effectively useless.

Still very cool to have enough open source tooling and a PDK so this can even be attempted as a piece of open source design work!