Saw on the TTL'ers char group that the analysis and sim package Micro-Cap 12 is free and has a load of 74xx components in the library as well as analogue stuff, so I decided to have a look.

I was pleased to see that components like the 74HCT4017 and even the 74HCT670 register file are in there which is excellent and surprising.

As an experiment I built a trivial sim using the 74HCT4017 phaed clock generator and noticed that the sim was showing some behaviour that my own Verilog sim wasn't; MicroCap looked correct.

It turned out that I'd forgotten to include the timing delays in my 74HCT4017 verilog model. So I'll probably spend a little more time messing with MicroCap, though I don't know if I have the stamina for a full blown sim.

Definitiely worth a look though (interface takes a bit of getting used to).