I tried to build a kernel for a SS470, to try out the SUN4_MMU3L and
see what it did.

I took GENERIC, turned on SUN4_MMU3L, and went through and stripped out
some options I was sure I didn't want and all sbus and iommu busses
(and everything orphaned thereby).  When I tried to build the result,
it ticked along nicely until link time, when it fell over:

ld -N -p -Ttext F0004000 -e start -X -o netbsd ${SYSTEM_OBJ} vers.o
../../../../arch/sparc/dev/obio.c:178: Undefined symbol `_sbus_attach' referenced from text segment
../../../../arch/sparc/dev/dma.c:115: Undefined symbol `_sbus_print' referenced from text segment
../../../../arch/sparc/dev/dma.c:240: Undefined symbol `_sbus_establish' referenced from text segment
../../../../arch/sparc/dev/dma.c:247: Undefined symbol `_sbus_setup_attach_args' referenced from text segment
../../../../arch/sparc/dev/dma.c:250: Undefined symbol `_sbus_destroy_attach_args' referenced from text segment
../../../../arch/sparc/dev/esp.c:292: Undefined symbol `_sbus_establish' referenced from text segment
../../../../arch/sparc/dev/esp.c:345: Undefined symbol `_sbus_establish' referenced from text segment
../../../../arch/sparc/dev/bwtwo.c:301: Undefined symbol `_sbus_establish' referenced from text segment
../../../../arch/sparc/dev/cgsix_sbus.c:177: Undefined symbol `_sbus_establish' referenced from text segment
../../../../arch/sparc/sparc/cache.c:201: Undefined symbol `_dvma_cachealign' referenced from text segment
../../../../arch/sparc/sparc/cache.c:204: Undefined symbol `_dvma_cachealign' referenced from text segment

Is it just not possible to build a SPARC kernel without SBus support?
That's what it looks like.  (I'm trying again, with GENERIC modified
only by turning on SUN4_MMU3L.)

Here's the whole config file that produced the broken kernel.  (The
source tree was supped 1998-08-03 - I haven't quite dared track
-current with all the stuff currently in flux.  While I do have some
patches, I don't believe I have any that have any bearing on this.)

# 	$NetBSD: GENERIC,v 1.69 1998/07/23 13:03:23 pk Exp $

include "arch/sparc/conf/std.sparc"

maxusers	32

## System kernel configuration.  See options(4) for more detail.


# Options for variants of the Sun SPARC architecure.
# We currently support three architecture types; at least one is required.
options 	SUN4		# sun4/100, sun4/200, sun4/300
options 	SUN4C		# sun4c - SS1, 1+, 2, ELC, SLC, IPC, IPX, etc.
options 	SUN4M		# sun4m - SS10, SS20, Classic, etc.

options 	SUN4_MMU3L	# 3-level MMU on sun4/400; (incomplete)

## System options specific to the sparc machine type

# Blink the power LED on some machines to indicate the system load.
#options 	BLINK

## Use a faster console than the PROM's slow drawing routines.  Not needed
## for headless (no framebuffer) machines.
#options 	RASTERCONSOLE	# fast rasterop console
#options 	RASTERCONS_WONB
#options 	RASTERCONS_SMALLFONT
#options 	RASTERCONS_FULLSCREEN

#### System options that are the same for all ports

## Root device configuration: change the ?'s if you are going to use a
## nonstandard root partition (other than where the kernel is booted from)
## and/or nonstandard root type (not ffs or nfs).  Normally this can be
## automagically determined at boot time.

config		netbsd	root on ? type ?

## System call tracing (see ktrace(1)).
options 	KTRACE

## Collect statistics on kernel malloc's and free's.  This does have a
## significant performance hit on slower machines, so it is intended for
## diagnostic use only.
#options 	KMEMSTATS

## System V compatible IPC subsystem.  (msgctl(2), semctl(2), and shmctl(2))
options 	SYSVMSG		# System V message queues
options 	SYSVSEM		# System V semaphores
options 	SYSVSHM		# System V shared memory
#options 	SHMMAXPGS=1024	# 1024 pages is the default

## Loadable kernel module support; still under development.
#options 	LKM

## NFS boot options; default on sparc is the bootparam protocol
#options 	NFS_BOOT_BOOTPARAM
#options 	NFS_BOOT_BOOTP
#options 	NFS_BOOT_DHCP

#### Debugging options

## The DDB in-kernel debugger runs at panic (unless DDB_ONPANIC=0), or at
## serial console break or keyboard reset, where the PROM would normally
## intercept.  DDB_HISTORY_SIZE adds up/down arrow command history.
options 	DDB			# kernel dynamic debugger
#options 	DDB_HISTORY_SIZE=100	# enable history editing in DDB
options 	DDB_ONPANIC=1		# see also sysctl(8): `ddb.onpanic'

## You may also use gdb, on another computer connected to this machine over
## a serial port.  Both KGDBDEV and KGDBRATE should be specified; KGDBDEV is
## a dev_t encoded device number of the serial port to use.
## (0xc01 = ttya, 0xc02 = ttyb.)
#options 	KGDB		# support for kernel gdb
#options 	KGDBDEV=0xc01	# kgdb device number (this sample is `ttyb')
#options 	KGDBRATE=38400	# baud rate


## Compile the kernel with debugging symbols (`netbsd.gdb' is the debug file),
## such that gdb(1) can be used on a kernel coredump.

makeoptions 	DEBUG="-g"

## Adds code to the kernel that does internal consistency checks, and will
## cause the kernel to panic if corruption of internal data structures
## is detected.
options 	DIAGNOSTIC	# extra kernel sanity checking

## Enable (possibly expensive) debugging code that may also display messages
## on the system console
options 	DEBUG

## Make SCSI error messages more verbose when explaining their meanings.
options 	SCSIVERBOSE

## `INSECURE' turns off the kernel security level (securelevel = 0 always).
## This allows writing to /dev/mem, loading kernel modules while multi-user,
## and other insecurities good only for development work.  Do not use this
## option on a production machine.
#options 	INSECURE

## Allow non-root users to grab /dev/console with programs such as xconsole.
## `xconsole' therefore does not need setuid root with this option enabled.
#options 	UCONSOLE

## `FDSCRIPTS' allows non-readable but executable scripts by providing a
## pre-opened opaque file to the script interpreter.  `SETUIDSCRIPTS',
## which implies FDSCRIPTS, allows scripts to be set-user-id using the same
## opaque file mechanism.  Perl calls this "secure setuid scripts."

#options 	FDSCRIPTS
#options 	SETUIDSCRIPTS

## Options for compatibility with previous releases foreign system binaries.
## In the cases of COMPAT_SUNOS and COMPAT_SVR4, you may need to set up
## additional user-level utilities or system configuration files. See
## compat_sunos(8) and compat_svr4(8).

options 	COMPAT_43	# 4.3BSD system interfaces
options 	COMPAT_10	# NetBSD 1.0 binary compatibility
options 	COMPAT_11	# NetBSD 1.1 binary compatibility
options 	COMPAT_12	# NetBSD 1.2 binary compatibility
options 	COMPAT_13	# NetBSD 1.3 binary compatibility
options 	COMPAT_SUNOS	# SunOS 4.x binary compatibility
options 	COMPAT_SVR4	# SunOS 5.x binary compatibility
options 	EXEC_ELF32	# Exec module for SunOS 5.x binaries.

## File systems.  You probably need at least one of FFS or NFS.
file-system	FFS		# Berkeley Fast Filesystem
file-system	NFS		# Sun NFS-compatible filesystem client
file-system	KERNFS		# kernel data-structure filesystem
file-system	NULLFS		# NULL layered filesystem
file-system	MFS		# memory-based filesystem
file-system	FDESC		# user file descriptor filesystem
#file-system	UMAPFS		# uid/gid remapping filesystem
#file-system	LFS		# Log-based filesystem (still experimental)
#file-system	PORTAL		# portal filesystem (still experimental)
file-system	PROCFS		# /proc
file-system	CD9660		# ISO 9660 + Rock Ridge file system
file-system	UNION		# union file system
#file-system	MSDOSFS		# MS-DOS FAT filesystem(s).

## File system options.
#options 	NFSSERVER	# Sun NFS-compatible filesystem server
#options 	QUOTA		# FFS quotas
options 	FFS_EI		# FFS Endian Independent support

## Network protocol support.  In most environments, INET is required.
options 	INET		# IP (Internet Protocol) v4
options 	TCP_COMPAT_42	# 4.2BSD IP implementation compatibility
#options 	GATEWAY		# packet forwarding ("router switch")
#options 	MROUTING	# packet forwarding of multicast packets
#options 	DIRECTED_BROADCAST	# allow broadcasts through routers
#options 	NS		# Xerox NS networking
#options 	NSIP		# Xerox NS tunneling over IP
#options 	ISO,TPIP	# OSI networking
#options 	EON		# OSI tunneling over IP
#options 	CCITT,LLC,HDLC	# X.25 packet switched protocol
#options 	NETATALK	# AppleTalk (over Ethernet) protocol
options 	NTP		# Network Time Protocol in-kernel support
#options 	PPS_SYNC	# Add serial line synchronization for NTP
#options 	PFIL_HOOKS	# Add pfil(9) hooks, intended for custom LKMs.
#options 	IPFILTER_LOG	# Add ipmon(8) logging for ipfilter device
#options 	PPP_BSDCOMP	# Add BSD compression to ppp device
#options 	PPP_DEFLATE	# Add deflate (libz) compression to ppp device
#options 	PPP_FILTER	# Add active filters for ppp (via bpf)
#options 	FORCE_TCP_KEEPALIVES

#### Main bus and CPU .. all systems.
mainbus0 at root
cpu0	at mainbus0

#### Bus types found on SPARC systems.

#sbus0	at mainbus0				# sun4c
obio0	at mainbus0				# sun4 and sun4m
vme0	at mainbus0				# sun4
#iommu0	at mainbus0				# sun4m
#sbus0	at iommu0				# sun4m
#vme0	at iommu0				# sun4m

## SBus expander box
#xbox*	at sbus? slot ? offset ?
#sbus*	at xbox?

#### Standard system devices -- all required for a given architecture

## Auxiliary system registers on sun4c and sun4m
auxreg0	at mainbus0				# sun4c
auxreg0	at obio0				# sun4m

## Power status and control register on Sun4m systems
power0	at obio0

## Mostek clock found on 4/300, sun4c, and sun4m systems.
## The Mostek clock NVRAM is the "eeprom" on sun4/300 systems.
clock0	at mainbus0				# sun4c
clock0	at obio0				# sun4m
clock0	at obio0 addr 0xf2000000		# sun4/300

## Intersil clock found on 4/100 and 4/200 systems.
oclock0	at obio0 addr 0xf3000000		# sun4/200
oclock0	at obio0 addr 0x03000000		# sun4/100

## Memory error registers.
memreg0	at mainbus0				# sun4c
memreg0	at obio0				# sun4m
memreg0	at obio0 addr 0xf4000000		# sun4/200 and sun4/300
memreg0	at obio0 addr 0x04000000		# sun4/100

## Timer chip found on 4/300, sun4c, and sun4m systems.
timer0	at mainbus0				# sun4c
timer0	at obio0				# sun4m
timer0	at obio0 addr 0xef000000		# sun4/300

## EEPROM found on 4/100 and 4/200 systems.  Note that the 4/300
## doesn't use this driver; the `EEPROM' is in the NVRAM on the
## Mostek clock chip on 4/300 systems.
eeprom0	at obio0 addr 0xf2000000		# sun4/200
eeprom0	at obio0 addr 0x02000000		# sun4/100


#### Serial port configuration

## Zilog 8530 serial chips.  Each has two-channels.
## zs0 is ttya and ttyb.  zs1 is the keyboard and mouse.
zs0	at mainbus0					# sun4c
zs0	at obio0					# sun4m
zs0	at obio0 addr 0xf1000000 level 12 flags 0x103	# sun4/200 and sun4/300
zs0	at obio0 addr 0x01000000 level 12 flags 0x103	# sun4/100
zstty0	at zs0 channel 0	# ttya
zstty1	at zs0 channel 1	# ttyb

zs1	at mainbus0					# sun4c
zs1	at obio0					# sun4m
zs1	at obio0 addr 0xf0000000 level 12 flags 0x103	# sun4/200 and sun4/300
zs1	at obio0 addr 0x00000000 level 12 flags 0x103	# sun4/100
kbd0	at zs1 channel 0	# keyboard
ms0	at zs1 channel 1	# mouse

zs2	at obio0 addr 0xe0000000 level 12 flags 0x103	# sun4/300
zstty2	at zs2 channel 0	# ttyc
zstty3	at zs2 channel 1	# ttyd


## Magma Serial/Parallel driver
#magma*	at sbus? slot ? offset ?
#mtty*	at magma?
#mbpp*	at magma?


#### Disk controllers and disks

#

## The following flags may be set for the NCR53c94 based esp driver:
##	bits 0-7:  disable disconnect/reselect for the corresponding target
##	bits 8-15: disable synchronous negotiation for target [bit-8]

## sun4/300, sun4c, sun4m on-board SCSI, and FSBE/S SBus SCSI cards.
## Both `dma' and `esp' are needed in all cases.
## Two kinds of additional SBus SCSI interfaces are available.  One uses
## "esp at sbus" like the sun4c on-board; the other uses "esp at dma".

## sun4/300 SCSI - an NCR53c94 or equivalent behind
## an LSI Logic DMA controller

dma0	at obio0 addr 0xfa001000 level 4		# sun4/300
esp0	at obio0 addr 0xfa000000 level 4 flags 0x0000	# sun4/300

#dma0	at sbus0 slot ? offset ?			# sun4c/sun4m
#esp0	at sbus0 slot ? offset ? flags 0x0000		# sun4c
esp0	at dma0 flags 0x0000				# sun4m

# FSBE/S SCSI
#dma*	at sbus? slot ? offset ?			# SBus
#esp*	at sbus? slot ? offset ? flags 0x0000		# SBus (older proms)
esp*	at dma? flags 0x0000				# SBus

scsibus* at esp?

## Qlogic ISP SBus SCSI Card
#isp*	at sbus? slot ? offset ?
#scsibus* at isp?

## NCR5380-based "Sun SCSI 3" VME SCSI controller.
## This driver has several flags which may be enabled by OR'ing
## the values and using the "flags" directive.
## Valid flags are:
##
##	0x01		Use DMA (may be polled)
##	0x02		Use DMA completion interrupts
##	0x04		Allow disconnect/reselect
##
## E.g. the following would enable DMA, interrupts, and reselect:
## si0	at vme0 addr 0x200000 level 3 vect 0x40 flags 0x07
##
## By default, DMA is enabled in the driver.

si0	at vme0 addr 0x200000 pri 2 vec 0x40
scsibus* at si?

## NCR5380-based "SCSI Weird" on-board SCSI interface found
## on sun4/100 systems.  The flags are the same as the "si"
## controller.  Note, while DMA is enabled by default, only
## polled DMA works at this time, and reselects do not work
## on this particular controller.

sw0	at obio0 addr 0x0a000000 level 3
scsibus* at sw?

## These entries find devices on all SCSI busses and assign
## unit numbers dynamically.
sd*	at scsibus? target ? lun ?		# SCSI disks
st*	at scsibus? target ? lun ?		# SCSI tapes
cd*	at scsibus? target ? lun ?		# SCSI CD-ROMs
ch*	at scsibus? target ? lun ?		# SCSI changer devices
ss*	at scsibus? target ? lun ?		# SCSI scanners
uk*	at scsibus? target ? lun ?		# unknown SCSI


## Xylogics 753 or 7053 VME SMD disk controllers and disks, found
## on sun4 systems.
xdc0	at vme0 addr 0xee80 pri 3 vec 0x44
xdc1	at vme0 addr 0xee90 pri 3 vec 0x45
xdc2	at vme0 addr 0xeea0 pri 3 vec 0x46
xdc3	at vme0 addr 0xeeb0 pri 3 vec 0x47
xd*	at xdc? drive ?

## Xylogics 451 or 451 VME SMD disk controllers and disks, found
## on sun4 systems.
xyc0	at vme0 addr 0xee40 pri 3 vec 0x48
xyc1	at vme0 addr 0xee48 pri 3 vec 0x49
xy*	at xyc? drive ?


## Floppy controller and drive found on SPARCstations.

#fdc0	at mainbus0				# sun4c controller
#fdc0	at obio0				# sun4m controller
#fd*	at fdc0					# the drive itself

## A disk-like interface to files.  Can be used to create floppy, CD,
## miniroot images, etc.

pseudo-device	vnd	4

## Concatenated and striped disks; with this, you can create a software-based
## disk array similar to a "RAID 0" setup.  See ccd(4).

pseudo-device	ccd	4

## Memory disk device, used on boot floppies with compressed
## kernel-plus-root-disk images.

#pseudo-device	md	1


#### Network interfaces

## LANCE Ethernet - an AMD 7990 LANCE behind specialized DMA glue
## Three flavors of additional SBus ethernets are available.  One attaches
## directly like the sun4c on-board, one uses the ledma device like the
## sun4m on-board, and one uses the lebuffer device.

le0		at obio0 addr 0xf9000000 level 6	# sun4/300
#le0		at sbus0 slot ? offset ?		# sun4c on-board
#ledma0		at sbus0 slot ? offset ?		# sun4m on-board
#le0		at ledma0				# sun4m on-board
#le*		at sbus? slot ? offset ?		# SBus
#ledma*		at sbus? slot ? offset ?		# SBus
#le*		at ledma?				# SBus
#lebuffer0	at sbus? slot ? offset ?		# SBus
#le0		at lebuffer?				# SBus
#lebuffer*	at sbus? slot ? offset ?		# SBus
#le*		at lebuffer?				# SBus


## sun4/100 and sun4/200 Ethernet - an Intel 82586 on-board
## or on a Multibus/VME card.
ie0	at obio0 addr 0xf6000000 level 6		# sun4/200 on-board
ie0	at obio0 addr 0x06000000 level 6		# sun4/100 on-board
ie1	at vme0 addr 0xe88000 pri 3 vec 0x75		# VME
ie2	at vme0 addr 0x31ff02 pri 3 vec 0x76		# VME
ie3	at vme0 addr 0x35ff02 pri 3 vec 0x77		# VME
ie4	at vme0 addr 0x2dff02 pri 3 vec 0x7c		# VME

## Loopback network interface; required
pseudo-device	loop

## SLIP and CSLIP interfaces, for IP over a serial line.
pseudo-device	sl		2

## PPP, the successor to SLIP.  See pppd(8).
pseudo-device	ppp		4

## Starmode Radio IP, a special hardware network device.
#pseudo-device	strip		1

## Network "tunnel" device, allowing protocol stacks to run in the userland.
## This is used by the third-party user-mode "ppp" program, and others.
pseudo-device	tun		4

## Berkeley Packet Filter, required to run RARPD.  A generic C-language
## interface that allows selective examining of incoming packets.
pseudo-device	bpfilter	8

## IP Filter, used in firewall and NAT applications.  See ipnat(8) for
## one example of the use of the IP Filter.
#pseudo-device	ipfilter


#### Audio and video devices

## /dev/audio support (`audioamd' plus `audio')
##
audioamd0	at mainbus0				# sun4c
#audioamd0	at obio0				# sun4m
#audioamd0	at sbus0 slot ? offset ?		# sun4m
audio*		at audioamd0


## Sun "bwtwo" black and white framebuffer, found on sun4, sun4c, and sun4m
## systems.  If your sun4 system has a cgfour installed in the P4 slot,
## the P4 entries for "bwtwo" will attach to the overlay plane of the
## "cgfour".

#bwtwo0		at sbus0 slot ? offset ?		# sun4c and sun4m
#bwtwo*		at sbus? slot ? offset ?		#
bwtwo0		at obio0 addr 0xfd000000 level 4	# sun4/200
bwtwo0		at obio0 addr 0xfb300000 level 4	# sun4/300 in P4 slot
bwtwo0		at obio0 addr 0x0b300000 level 4	# sun4/100 in P4 slot

## Sun "cgtwo" VME color framebuffer
cgtwo0		at vme0 addr 0x400000 pri ? vec 0xa8

## Sun "cgthree" Sbus color framebuffer
#cgthree0	at sbus? slot ? offset ?
#cgthree*	at sbus? slot ? offset ?
#cgthree0	at obio? slot ? offset ?		# sun4m

## Sun "cgfour" color framebuffer with overlay plane.  See above comment
## regarding overlay plane.
cgfour0		at obio0 addr 0xfb300000 level 4	# sun4/300 P4
cgfour0		at obio0 addr 0x0b300000 level 4	# sun4/100 P4

## Sun "cgsix" accelerated color framebuffer.
#cgsix0		at sbus? slot ? offset ?
#cgsix*		at sbus? slot ? offset ?
cgsix0		at obio0 addr 0xfb000000 level 4	# sun4/300 P4
cgsix0		at obio0 addr 0x0b000000 level 4	# sun4/100 P4

## Sun "cgeight" 24-bit framebuffer
cgeight0 	at obio0 addr 0xfb300000 level 4	# sun4/300 P4
cgeight0	at obio0 addr 0x0b300000 level 4	# sun4/100 P4

## Sun "tcx" accelerated color framebuffer.
#tcx0		at sbus? slot ? offset ?
#tcx*		at sbus? slot ? offset ?

# Sun "cgfourteen" accelerated 24-bit framebuffer.
cgfourteen0	at obio0			# sun4m


#### Other device configuration

## Pseudo ttys, required for network logins and programs like screen.
## 32 is a good number for average systems; you may have as many as you
## like, though 256 is more or less the upper limit.  Increasing this
## number still requires you to run /dev/MAKEDEV to create the files
## for the ptys.

pseudo-device	pty		64	# pseudo-ttys (for network, etc.)

## Random device, used to implement /dev/random (a source of random noise),
## and generate randomness for some kernel formulae.
## THIS DEVICE IS EXPERIMENTAL; use at your own risk.

pseudo-device	rnd

					der Mouse

			       mouse@rodents.montreal.qc.ca
		     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B