Are autorouters a good idea for me?
Autorouters are kind of ok as long as you have a smallish number of traces or only non critical traces. And i am sure they are better suited for low density boards than the more modern high density boards.
8MHz is also not the only parameter that is important when talking about digital signals like an SPI. How fast is your switching time? (dV/dt)
How long is the SPI? Is more than one device on it? Can you already see how the traces should look like before even starting the router? … The answers of all these will change how well the autorouter is suited for the task.
And possibly the most important question of all: How strict are the EMC requirements? Does your system need to be tested against some standard or does it only need to work in laboratory environments?
- For the later: Who the hell cares as long as it works. (Well a perfectionist like me will. But that is a different story.)
- For the former: You want it to be first time right as the guys that test your stuff are quite expensive. (And consider the time lost by multiple iterations.) So better invest more time into it than clicking autoroute. (Meaning one would use it at most as a first iteration.)
Does kicad come with an inbuild autorouter?
No it does not. It had a primitive one in the past but that only worked in the legacy toolset and it was simply not worth transferring it over to the new toolset.
There is an interface to an external autorouter available. (freerouter via the spectra DSN export/import. And there is a python plugin somewhere that does offer easier access. See: Announcing kicad_freerouting-plugin)
That one can sadly not be integrated at all as it is not 100% clear that everything is ok with its licensing (There is some sort of dispute going on but i am not really sure who exactly is involved.) Another problem is that it is written in java and no longer fully maintained making it even less likely to be included into kicad.
There are however vague plans to maybe at least include a basic autorouter again sometime in the future. (And i am sure nobody would have anything against a volunteer investing time into this. It simply is not a priority for the core team as they want to aim kicad at high end professional use. Autorouters simply are not there yet to fulfill these usecases so there is no real need to invest time into them.)
And shameless plug: https://contextualelectronics.com/product/never-trust-the-autorouter-t-shirt/