> 
> would have thought it would be easy enough for the i386 port to reserve a block
> of physical memory at boot time which is then used for a DMA bounce buffer. The
> only things which would need changing this way are specific to the port or
> drivers. In other words it isn't a job for the core, but for the i386 port
> maintainer. Am I missing something?
> 
No. This is a way to solve it once and for ever regarding the adaptec board.
Thus only those with aha1542 boards and ram >16Mb would "suffer" but NetBSD
would be usable for many matching this config.