[SI-LIST] Re: OT: Overvoltage breakdown on 120 nm silicon?
- From: Dimiter Popoff <dp@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Thu, 17 Feb 2011 19:09:02 +0200
Well not that I could rule this out but it does not look much
like it. It appears that the core is failing - which is powered
off the 1.5V, this is internal only (no inputs/outputs).
Then the consumption did not change. Then I have overvoltage
protection on each of the power lines - 1.5, 2.5 and 3.3
(SCR with zener for the 2.3 and 3.3, the 1.5 somewhat different
but in effect that again - so the spikes were really well limited
in both height and in time).
And then the DDR works - -2.5V powered. So does the flash and the
ATA interface - 3.3V powered...
But I am really inexperieced with failed parts of that size/complexity
so I don't know, I feel really clueless. I will replace the CPU at
some point (when I get some, I am out of parts now) but it is
just interesting to me what this can be, I have seen a CPU
which failed at some opcode 25 years ago, once (a clone of
the 6800). And while it cost me some time to catch that I could
catch where it failed. On that PPC part now things are incomparably
more complex, nothing is guaranteed to be in order, caches, MMU,
you name it. But I have done all the low and high level stuff so
I can say I have narrowed things down - yet I could
not catch the access which fails. Putting a breakpoint within a section of
say 20 opcodes prior to a certain location makes the return
address on the stack correct (a breakpoint does an illegal opcode
exception, tons of processing/memory i/o, possibly cache
flushes etc.). Put it below a certain opcode - no opcode doing
anything of interest - and the stacked return address is bad...
It _does_ sound so much like a software issue yet it is limited to
that board only.
I spent over a day only recalling things so I could ensure there was
no exception taking place to cause the failure. I think I have run
out of ideas now though...
Dimiter
------------------------------------------------------
Dimiter Popoff Transgalactic Instruments
http://www.tgi-sci.com
------------------------------------------------------
http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/
>Subject: [SI-LIST] Re: OT: Overvoltage breakdown on 120 nm silicon?
>From: Russel Hughes <russel.hughes@xxxxxxxxx>
>To: Dimiter Popoff <dp@xxxxxxxxxxx>
>Cc: si-list@xxxxxxxxxxxxx
>Date: Thu, 17 Feb 2011 17:19:51 +0100
>
>ESD diodes on an input broken down? If you have put too much through them
>and they have shorted out it may explain your problem.
>Cheers
>
>Russel
>
>On 17 February 2011 16:44, Dimiter Popoff <dp@xxxxxxxxxxx> wrote:
>
>> I am facing an unbelievable reality at the moment.
>> A processor which will not boot - although all tests I have
>> done to it pass.
>>
>> I still refuse to believe I can have killed the CPU - but after
>> 3 days of tracing of the boot process I seem to run out of
>> other explanations (heck, I had to dig through code some of
>> which I have written 15+ years ago...).
>>
>> The CPU (an MPC5200B) appears to work - monitor via UART, even disk
>> I/O worked etc. - but it fails some way into the boot process.
>> This happened after I fixed the power up sequencing closer to
>> the specs :-).
>>
>> That board had been working for nearly a year before that, had survived
>> the development process (lots of programming/debugging and power on/off).
>> It had lived through all that with a nice spike on the 1.5V, 2.5V and 3.3V
>> upon poweron, perhaps 1 to 5mS over the absolute maximum by perhaps
>> 50%. I changed that now - and it won't boot, fails at more or less
>> the same place (pulls the wrong return address from the stack if I am
>> not tracing ....). This is after a few system calls have returned OK
>> already. It looks unbelievable to me to have killed the CPU in such
>> a subtle way - but I have not seen many killed ones.
>>
>> How likely is it that I have killed it? The only news about the
>> spikes which I believe to may have killed it is that I now know they
>> used to exist...
>> Not to speak of the other boards which keep on workingfine :).
>>
>> I also made the CPU check almost all of the 64M DDRAM, write address
>> to location/verify - works, did that with the written address rotated
>> 0 to 31 times, also works.... And all that also misaligned,
>> also works fine - it is pretty maddening really.
>>
>> I am simply clueless as to how likely it is to break a gate
>> with say 2.5V instead of 1.5? I guess drain/source breakdown won't
>> be an issue even if they break for a few mS (not enough energy
>> to fry anything)?
>>
>> Hopefully people with more silicon inside knowledge can
>> comment...
>>
>> Thanks,
>> Dimiter
>>
>> ------------------------------------------------------
>> Dimiter Popoff Transgalactic Instruments
>>
>> http://www.tgi-sci.com
>> ------------------------------------------------------
>> http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
