Finding valid nubus info at the end of Centris 650 ROM as Allen suggested,
I configured a kernel that would attempt to use it.

With DEBUG set in nubus.c, the following output was emitted:

probing slot 15, first probe at 0x408fffff (PA 0x0).
bytelanes of 0xf found for slot 0xf.
fmt->top is 0x0x9e83000, that minus 0x14 puts us at 0x0x9e82fec.
Directory offset 0xffff2cb8     Length 0x0      CRC 0x0
Revision level 0x1      Format 0x1      Test Pattern 0x5a932bc7
nubus0: slot f: Unknown Macintosh (Vendor: Apple Computer, Inc., Part: The
Horror ROM)  not configured

Anyone know if this is meaningful?  :-)

I was hoping that it would find the internal video.  I increased the
MAX_SLOT and then hard-coded a starting address for the "ROM slot" that
would find the byte lanes at 408fffff.  My patch (formatted to fit the
screen) is:

*** /usr/src/sys/arch/mac68k/dev/nubus.h        Tue May  7 07:27:26 1996
--- dev/nubus.h Sat Jun  8 16:01:32 1996
***************
*** 218,232 ****
  #define NUBUS_EXEC_CPU_68020  2
  #define NUBUS_EXEC_CPU_68030  3
  #define NUBUS_EXEC_CPU_68040  4

  #define NUBUS_MIN_SLOT                0x9
! #define NUBUS_MAX_SLOT                0xE
  #define NUBUS_ROM_TEST_PATTERN        0x5A932BC7

! #define NUBUS_SLOT_TO_PADDR(x)        ( 0xF9000000 + \
!                                ((((x)-NUBUS_MIN_SLOT) & 0xF) << 24))

  struct nubus_softc {
        struct  device  sc_dev;
  };

--- 218,236 ----
  #define NUBUS_EXEC_CPU_68020  2
  #define NUBUS_EXEC_CPU_68030  3
  #define NUBUS_EXEC_CPU_68040  4

  #define NUBUS_MIN_SLOT                0x9
! #define NUBUS_MAX_SLOT                0xF
  #define NUBUS_ROM_TEST_PATTERN        0x5A932BC7

! #define NUBUS_SLOT_TO_PADDR(x)  ( \
!                                 ((x) < NUBUS_MAX_SLOT) ? \
!                     (0xF9000000 + ((((x)-NUBUS_MIN_SLOT) & 0xF) << 24)) \
!                                 : \
!                     (0x3F900000)  )
!


--
John D. Smerdon;  Livonia, Michigan, USA;  Contents are my opinion.
Home: jds@smerdon.livonia.mi.us