If it helps to have a practical testimonial, I compiled my kernel with
DISABLE_EXT_CACHE commented out for my IIci (thus enabling it), running
an external cache, and the system seems to be perfectly stable.

Bill Studenmund wrote:
> 
> >
> > HI,
> >
> > I'm trying my hand at compiling a custom kernel, and wonder about some options I've seen around the net for Netbsd...
> >
> > I'd appreciate the time anyone takes to explain these.  Maybe the results can be put in the FAQ for kernel building?
> 
> Actually, many of the items are in man options. Ones which aren't there should
> get added to it.
> 
> To get a feel for what's changable and what's not, look at the GENERIC
> config and the other configs in /sys/arch/mac68k/conf. If something's
> duplicated in all of them, then chances are it's important.
> 
> > Thanks!
> >
> >
> > Is the IIci cache support unstable/experimental?
> > options         DISABLE_EXT_CACHE # Don't use IIci external cache

[snipped]

> 
> Recently it came up that this option is probably no longer needed.
>