I incorporated the changes suggested by Walter Ruetten regarding
emptying the Egret ADB into my source tree, and compiled on my IIsi.

The compile went fine except for the line:

	if (current_mac_model->class == MACH_CLASSIIsi)

which didn't compile because neither MACH_CLASSIIsi nor
current_mac_model were defined symbols ???  I'm not deep into this
enough yet to know where I screwed this up- so I replaced it with:

	if (1)

The results were almost identical to what Walter described for his
IIvi - as he predicted they would be. 

For the curious,
boot transcript follows:

[ preserving 74568 bytes of netbsd symbol table ]
DEBUG: Console initialized
Low = 0x4000000, high = 0x47f8000
Low = 0x50000, high = 0x58000
8388608 bytes available (2048 pages)
Log = 0xf9000000, Phys = 0xf9000000, Len = 0x5e00000 (98566144)
Log = 0xfee00000, Phys = 0x0, Len = 0xffff0000 (-65536)
Log = 0xfee10000, Phys = 0x8000, Len = 0x48000 (294912)
Log = 0xfee58000, Phys = 0x0, Len = 0xfff58000 (-688128)
Log = 0xfef00000, Phys = 0xfef00000, Len = 0x100000 (1048576)
  Video address = 0xfee08000
  Weird mapping starts at 0xfee08000
  Length = 0x50000 (327680) bytes
DEBUG: 68030 - MMU mapping parsed
DEBUG: Got memory size as passed from Booter
DEBUG: preparing new MMU context
DEBUG: clearing TT registers...
DEBUG: about to set MMU control (hold your breath)
DEBUG: yay!  MMU enabled with new mapping
DEBUG: MMU flushed.
DEBUG: calling pmap_bootstrap() ... done.
DEBUG: invalidating TLB
DEBUG: activating cache(s)
DEBUG: calling setmachdep() ... mrg: ROM adbintr 0x40814912
mrg: ROM pmintr 0x00000000
mrg: OS trap 0x77 (CountADBs) = 0x4080a360
mrg: OS trap 0x78 (GetIndADB) = 0x4080a37a
mrg: OS trap 0x79 (GetADBInfo) = 0x4080a3a6
mrg: OS trap 0x7a (SetADBInfo) = 0x4080a3ac
mrg: OS trap 0x7b (ADBReInit) = 0x4080a752
mrg: OS trap 0x7c (ADBOp) = 0x4080a3dc
mrg: OS trap 0x7c (PMgrOp) = 0x00000000
done.
DEBUG: enabling interrupts ... done.
DEBUG: away we go!
Copyright (c) 1982, 1986, 1989, 1991, 1993
	The Regents of the University of California.  All rights reserved.

NetBSD 1.0 (MRGDEBUG) #0: Mon Jan  2 14:53:22 PST 1995
    root@:/usr/src/sys/arch/mac68k/compile/MRGDEBUG
Apple Macintosh IIsi  (68030)
real mem = 75493376
avail mem = 5316608
using 204 buffers containing 835584 bytes of memory
mrg: 'Mac IIsi class ROMs' rom glue, tracing off, debug on, silent traps
mrg: start init
After setting globals
after setting jump points
mrg: end init
adb: bus subsystem
adb: call mrg_initadbintr
adb: returned from mrg_initadbintr
adb: empty ADB chip
adb: calling ADBReInit
mrg: a super wd 0xa07b OS # 0x7b addr 0x4080a752
mrg: a super wd 0xa092 OS # 0x92 addr 0x40814800
 bk exit
mrg: a super wd 0xa092 OS # 0x92 addr 0x40814800
 bk exit
mrg: a super wd 0xa092 OS # 0x92 addr 0x40814800
 bk exit
mrg: a super wd 0xa092 OS # 0x92 addr 0x40814800
 bk exit
mrg: a super wd 0xa092 OS # 0x92 addr 0x40814800
 bk exit
mrg: a super wd 0xa092 OS # 0x92 addr 0x40814800
 bk exit
mrg: a super wd 0xa092 OS # 0x92 addr 0x40814800
 bk exit

...

This message then repeats itself until it overruns
the 9600 baud serial line.  Sometime after that it 
hangs.