Problems upgrading a Sun3/160 to OS 4.0

[Kathryn Smith]

I recently tried to upgrade a Sun 3/160 system to OS 4.0.  This is not the
first upgrade to 4.0 which I've performed, so I'm reasonably sure of the
procedures.  I get to the point of trying to boot either the mini-root, or 
the munix, and neither will boot successfully.  They boot down through the
point of listing all the devices present on the system and the "root on xy0b,
swap on xy0b" messages, then die with the following messages

swap on xy0b fstype spec 16756K
dump on xy0b fstype spec

trap address 0x8, pid 1 pc=f055cde, sr=2010, stkfmt b, contact 1
Bus Error Reg 20<TIMEOUT>
data fault address 10180ea0 faultc 0 faultb 0 dfault1 rw 1 size 0 fcode 5
KERNEL MODE
	[ register dump and trace back ]

The hardware is as follows:

	Sun 3/160, currently running OS 3.5 without difficulty
	1 Fujitsu M2333 disk on a Xylogics 451 controller
	cartridge tape unit

	Prom level: 1.8

I called Sun for software support, and talked to someone who seemed barely
able to take down the error messages, and didn't seem to have any clue
what they meant, judging from the things she asked me to spell, spent 10
minutes looking up things while I sat on hold, and then told me I must
have an old revision CPU, and should place a hardware call, since if I
knew the tape was good, there couldn't be any other reason why it wouldn't
work on my machine, unless of course I had the wrong tape.  (Never mind
that things like the standalone copy program shouldn't work either in that
case).  Needless to say, I'm not impressed, and I'm hoping that perhaps
someone out there has already run into this problem.

I don't want to place a hardware call because we do self-maintenance here,
and a 24 hr. exchange on a CPU board is a large chunk of money to pay out
to find out that I'm being given a run-around by someone in software
support who doesn't really know what they're doing.  

Please respond via private e-mail, and I will summarize for everyone if I
get any useful information from this.

Thanks in advance,
Kathryn Smith