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Are there any emulators out there that provide accurate USB model (timings, bus, checks and all)?
Maybe not as much x86 virtual machine, but specific host controller simulators?
There got to be some tools people use to plan and develop USB hardware, no?

The only thing close enough i found is Simics, but they don't give evaluation versions any more.

There were several projects of making Bochs an OSDEV-grade emulator, petr-bochs and rebochs i think, none anywhere close to completion.
Were there any tries before?

Basically, anything that can give verbose description of the errors happening down in the hardware.

You are right that my rebochs is intended to get there someday, but is nowhere near completion. One of the reasons that I started the project is that AFAIK the answer to your question is "no".

The closest you'll get is VMware - and you still don't have timing issues or the other cascade of potential problems you could expect from physical hardware.