CDROM Unknown Transfer Error crashes system

Wayne Witzke wwitzke at
Thu Oct 13 06:19:25 PDT 2005

Lowell Gilbert wrote:
> Wayne Witzke <wwitzke at> writes:
>>I'm a little confused...  I thought I had RELENG_5_4.  "uname -a" says:
>>FreeBSD wlaptop 5.4-RELEASE FreeBSD 5.4-RELEASE #1: Thu Oct  6
>>21:18:29 EDT 2005
>>      root at wlaptop:/usr/obj/usr/src/sys/WLAPTOP  i386
>>Isn't this RELENG_5_4?
> It was, but some patches have been applied since the release was
> made.  I was suggesting RELENG_5, not RELENG_5_4; in other words, the
> branch that will eventually become the 5.5 release.

I'll see if I can't figure out how to do this, then.  I had no idea that 
I wasn't running the most current.

>>Lowell Gilbert wrote:
>>>>Is there anything that I can do to capture more information the next
>>>>time my computer reboots spontaneously?
>>>Try to get a crash dump.  There's more information on it in the
>>>Handbook.  And some related information on panic analysis (if you can
>>>get it to that point) in the FAQ.
>>I'll try that, it doens't sound too difficult.  Just so I know, if I
>>was going to see a kernel panic message, I'd be seeing one before the
>>computer reboots, right?
> I thought that was what you were describing in earlier messages.

I'm *NOT* getting anything of this form (from the FAQ):

	Fatal trap 12: page fault while in kernel mode
	fault virtual address   = 0x40
	fault code              = supervisor read, page not present
	instruction pointer     = 0x8:0xf014a7e5
	stack pointer           = 0x10:0xf4ed6f24
	frame pointer           = 0x10:0xf4ed6f28
	code segment            = base 0x0, limit 0xfffff, type 0x1b
	                        = DPL 0, pres 1, def32 1, gran 1
	processor eflags        = interrupt enabled, resume, IOPL = 0
	current process         = 80 (mount)
	interrupt mask          =
	trap number             = 12
	panic: page fault

All I get is the single line error message in the system log:

acd0: unknown transfer phase

and then the computer drops to a POST and reboots.  I see nothing on my 
screen between the error and the POST.

One of the diagnostic steps that the FAQ mentions is to trace the 
instruction pointer.  My assumption was that if the system was going to 
give me a message like that, I'd see it before the POST, but I wanted to 
make sure that I didn't need to be looking for that message in a log 
somewhere, or changing a configuration option somewhere to make the 
system generate an error message of that form, because I definitely 
don't see that before the POST.


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