I haven't been following this lately, but from looking at
/usr/src/sys/dev/eisa/files.eisa and /usr/src/sys/conf/files, it appears that
there's a new amalgamated Adaptec 274X/284X/294X/394X/aic7770/aic78[5678]0
driver (from Justin Gibbs via Charles Hannum) that's just plain "ahc" now.

In my .../sys/arch/i386/conf, GENERIC, GENERICADP and INSTADP all still contain

ahe0		at isa? port 0x1c00 irq ?	# Adaptec 284x SCSI controllers
scsibus*	at ahe?

"GENERIC", "GENERICADP" and "INSTADP" should have been updated to remove these
now-dangling references to "ahe0".

This causes, e.g.

scipio# config INSTADP
INSTADP:93: ahe0: unknown device `ahe'
INSTADP:94: scsibus* at ahe?: `ahe' unknown
*** Stop.

My file dates are

-rw-r--r--  1 root  wheel    771 May 16 11:16 /usr/src/sys/dev/eisa/files.eisa
-rw-r--r--  1 root  wheel  10749 May 16 11:15 /usr/src/sys/conf/files
-rw-r--r--  1 root  wheel   6579 May  7 04:26 GENERICADP
-rw-r--r--  1 root  wheel   4255 May  7 04:26 INSTADP
-rw-r--r--  1 root  wheel   7165 May  7 04:26 GENERIC

(This is using sources sup'ed as of yesterday.  I was trying to build some
install floppies in /usr/src/distrib, since it looked like Perry's been busy
in there lately.)

	- Greg