After some cheating esp started to work with fas in 'relaxed' mode:
no sync negotiation, no tag queueing and 1.5K. yea! Pretty 
stable, I didn't tested it a lot but was able to newfs, untar
distribution some times.
I thought that it would be useful to move it to current, just move
without merge to see how it behaves. So I did, but it started getting
DMA errors, no right away but after a little while.
The driver seems useful under 1.5K (uh, cross my fingers),
I'm not clear what is better to do next: just continue with 1.5K,
move it to current first or what? Ideas? Seems that I shall continue
with 1.5K. 

Does anybody know easy way to track source-changes between 1.5K and current?
Or maybe somebody knows what changed around scsi driver since then?

Cheers,
	Andrey