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Picture the scene:
I get called to a PC that won't boot any more. I remove one of the PCI
cards, and suddenly the PC works perfectly. Hmm.
On closer inspection, one of the ICs on the PCI card looks... Well let's
put it this way. The writing appears to be scortched. The surface of the
IC is apparently damp with an oily liquid. There's a bulge in the
surface of the IC, together with a few small cracks.
Here's a question for you: Why would an IC suddenly do this?
[And more importantly, how in the name of God does a device which only
has access to a few milliwatts manage to get warm enough to physically
melt??]
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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"Invisible" <voi### [at] dev null> wrote in message
news:4831a342$1@news.povray.org...
> [And more importantly, how in the name of God does a device which only
> has access to a few milliwatts manage to get warm enough to physically
> melt??]
Have you touched a CPU/graphics card that's been running 30 min+ recently?
A few years back, Tom's Hardware did a test on one of the early Athlon 1 GHz
chips. They ran it without heatsink or fan to see how hot it could get.
They managed to ignite the motherboard in less than an hour (iirc)
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On Mon, 19 May 2008 16:56:47 +0100, Invisible wrote:
> Here's a question for you: Why would an IC suddenly do this?
Components fail - fact of life for digital electronics.
Could have been a spike from the power supply or a short in the system
somewhere. Or it could've been struck by lightning (had a computer once
that had that happen - the diagnosis was a list of components with
"fried" written next to each component).
Jim
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>> [And more importantly, how in the name of God does a device which only
>> has access to a few milliwatts manage to get warm enough to physically
>> melt??]
>
> Have you touched a CPU/graphics card that's been running 30 min+ recently?
Yeah, but the CPU and the GPU both have access to slightly more than a
few milliwatts. ;-)
[At least, I *presume* that's why my GPU requires no less than *two*
additional power supply connections...]
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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On Mon, 19 May 2008 18:15:16 +0100, Orchid XP v8 wrote:
> [At least, I *presume* that's why my GPU requires no less than *two*
> additional power supply connections...]
Try a component that's on an expansion card, then - I was working inside
one of my servers recently, and the MMU fan died - so I was messing about
with the connector while the power was on, and I noticed a fair bit of
heat coming from the ethernet card as well.
Jim
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Invisible wrote:
> Picture the scene:
>
> I get called to a PC that won't boot any more. I remove one of the PCI
> cards, and suddenly the PC works perfectly. Hmm.
>
> On closer inspection, one of the ICs on the PCI card looks... Well let's
> put it this way. The writing appears to be scortched. The surface of the
> IC is apparently damp with an oily liquid. There's a bulge in the
> surface of the IC, together with a few small cracks.
>
> Here's a question for you: Why would an IC suddenly do this?
>
Someone let the magic blue smoke out.
Seriously - Any number of things can cause a cascading effect. The card
has the +12v and +5v rails. If the chip or voltage regulator has
something go wrong, it can cause *unlimited* current & poof.
As to what initiated the event, that's any number of things.
The voltage regulator on the card on in the PS could have had a problem.
The chip could have had a design defect.
The chip could have just normally failed.
A voltage spike could have fried something.
A problem that happened long ago set up the failure, but it didn't
happen until now.
etc....
Tom
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"Jim Henderson" <nos### [at] nospamcom> wrote in message
news:4831ab8e$1@news.povray.org...
> Or it could've been struck by lightning (had a computer once
> that had that happen - the diagnosis was a list of components with
> "fried" written next to each component).
My parent's place got hit by lightning once many years back (back when
10-Base-2 was commonly used for networks)
Lightning directly hit the phone line that was connected to a modem. Modem
connected to PC, PC onto network cable that had 4 other machines attached.
We never found the modem, just some fragments strewn across the office.
Total casualties - 3 complete PCs, 1 network cable, 2 network cards, 1
modem.
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On Mon, 19 May 2008 21:58:09 +0200, Gail Shaw wrote:
> My parent's place got hit by lightning once many years back (back when
> 10-Base-2 was commonly used for networks) Lightning directly hit the
> phone line that was connected to a modem. Modem connected to PC, PC onto
> network cable that had 4 other machines attached.
Wow.
When I was in school in Florida, I had a Vendex V20-based PC (8088
compatible) that was thinking about its first move in a game of chess
(how many remember Sargon IV?); it'd been thinking for about 20 hours
(I'd set it to the hardest level). Thunderstorm rolled in, and a
lightning strike hit the power pole outside the window (took out the
transformer). I'm sure my PC wasn't the only casualty, but all the
pieces were still in the case when that was done...
Jim
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Jim Henderson wrote:
> On Mon, 19 May 2008 21:58:09 +0200, Gail Shaw wrote:
>
>> My parent's place got hit by lightning once many years back (back when
>> 10-Base-2 was commonly used for networks) Lightning directly hit the
>> phone line that was connected to a modem. Modem connected to PC, PC onto
>> network cable that had 4 other machines attached.
>
> Wow.
>
> When I was in school in Florida, I had a Vendex V20-based PC (8088
> compatible) that was thinking about its first move in a game of chess
> (how many remember Sargon IV?); it'd been thinking for about 20 hours
> (I'd set it to the hardest level). Thunderstorm rolled in, and a
> lightning strike hit the power pole outside the window (took out the
> transformer). I'm sure my PC wasn't the only casualty, but all the
> pieces were still in the case when that was done...
>
> Jim
I guess these are the reasons I unplug my computer from both wall and
phone line during a thunderstorm...
Sam
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On Mon, 19 May 2008 14:03:46 -0700, stbenge wrote:
> Jim Henderson wrote:
>> On Mon, 19 May 2008 21:58:09 +0200, Gail Shaw wrote:
>>
>>> My parent's place got hit by lightning once many years back (back when
>>> 10-Base-2 was commonly used for networks) Lightning directly hit the
>>> phone line that was connected to a modem. Modem connected to PC, PC
>>> onto network cable that had 4 other machines attached.
>>
>> Wow.
>>
>> When I was in school in Florida, I had a Vendex V20-based PC (8088
>> compatible) that was thinking about its first move in a game of chess
>> (how many remember Sargon IV?); it'd been thinking for about 20 hours
>> (I'd set it to the hardest level). Thunderstorm rolled in, and a
>> lightning strike hit the power pole outside the window (took out the
>> transformer). I'm sure my PC wasn't the only casualty, but all the
>> pieces were still in the case when that was done...
>>
>> Jim
>
> I guess these are the reasons I unplug my computer from both wall and
> phone line during a thunderstorm...
I haven't needed to since, though. Of course I've got two decent APC
UPSes here with insurance for the equipment. Doesn't replace the data,
but also living in the desert, we don't get many thunderstorms through
here. ;-)
Jim
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> [And more importantly, how in the name of God does a device which only has
> access to a few milliwatts manage to get warm enough to physically melt??]
Chips normally draw milliwatts, they have access to much more.
The power supply is something like 500+ watts transient until a
fuse pops or something. A soldering iron draws around 20 watts...
so if you are drawing 200 watts (normal operation) it's equivalent
to running 10 soldering irons.
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"stbenge" <stb### [at] hotmailcom> wrote in message
news:4831eb31@news.povray.org...
> I guess these are the reasons I unplug my computer from both wall and
> phone line during a thunderstorm...
>
> Sam
I started doing this after loosing a Kenwood AV controller and it was on a
GOOD surge protector.
Haven't lost any computers but the moment of first flicker everything gets
unplugged from the wall.
I guess that just proves that it's not nice to fool with mother nature!
Jim
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"stbenge" <stb### [at] hotmailcom> wrote in message
news:4831eb31@news.povray.org...
>
> I guess these are the reasons I unplug my computer from both wall and
> phone line during a thunderstorm...
My parent's house is at the top of a hill in a very open area. Until
recently their house was the highest thing for a couple km in any direction.
Add that to the frequency and intensity of thunderstorms in this part of the
world in summer and you see why they tended to get hit often.
They were very grateful when the neighbour put up a thatched roof and
installed a lightnng rod.
I live is a different area and I have 4 churches very near, all with
lighning rods. I seldom bother to unplug anything in a storm. So far, no
casualties from lighning
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> one of the PCI cards
...
> [And more importantly, how in the name of God does a device which only has
> access to a few milliwatts manage to get warm enough to physically melt??]
Where in the name of God did you get the idea that a PCI card only has
access to a few milliwatts? A quick Google told me the specification says
it can draw up to 25 W, so I imagine it can draw probably up to 30 W or more
on most motherboards.
30 W is easily enough to fry a chip.
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scott wrote:
> Where in the name of God did you get the idea that a PCI card only has
> access to a few milliwatts?
PCI devices are all extremely low power? Why would they design an
interface that can supply massively more power than necessary?
> A quick Google told me the specification
> says it can draw up to 25 W, so I imagine it can draw probably up to 30
> W or more on most motherboards.
>
> 30 W is easily enough to fry a chip.
Interesting - in my experiments, devices that are supposed to heat
things tend to be rated into kW...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> Interesting - in my experiments, devices that are supposed to heat things
> tend to be rated into kW...
See how long you can hold on to a 60 W light bulb for after you switch it
on...
Now imagine all that power concentrated into a tiny area inside a plastic
case.
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>> Interesting - in my experiments, devices that are supposed to heat
>> things tend to be rated into kW...
>
> See how long you can hold on to a 60 W light bulb for after you switch
> it on...
>
> Now imagine all that power concentrated into a tiny area inside a
> plastic case.
Mmm, crispy...
So, how come the entire board isn't melted? Just one little chip?
Presumably all that current had to get *in* to the board somehow...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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> So, how come the entire board isn't melted? Just one little chip?
> Presumably all that current had to get *in* to the board somehow...
Of course, but presumably the PCB tracks have low enough resistance not to
instantly melt the PCB when a couple of amps goes through them. The same
can't be said for the tiny tiny wires inside an IC. Remember, heating is
due to power not current.
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On Tue, 20 May 2008 11:46:48 +0200, "scott" <sco### [at] scottcom> wrote:
>Remember, heating is
>due to power not current.
>
P = I^2 * R :)
--
Regards
Stephen
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scott wrote:
> Remember, heating is due to power not current.
That's interesting - this is the first I've heard of this. I thought
*all* electric effects are due to current?
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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>> Remember, heating is due to power not current.
>
> That's interesting - this is the first I've heard of this.
It's simple physics, any electrical energy lost inside a component must be
converted to some other form of energy, usually the majority of which is
heat. The electrical energy lost inside a component does not depend solely
on current, but on power.
Example 1: 10 amps going through a thick cable of resistance .001 ohms.
Power dissipated = 1 W. Heating effect: very small
Example 2: 10 amps going through a heating element of resistance 10 ohms.
Power dissipated = 1000 W. Heating effect: a warm room.
You can compare those examples to the tracks on your PCB and the IC.
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Invisible wrote:
> Picture the scene:
>
> I get called to a PC that won't boot any more. I remove one of the PCI
> cards, and suddenly the PC works perfectly. Hmm.
>
> On closer inspection, one of the ICs on the PCI card looks... Well let's
> put it this way. The writing appears to be scortched. The surface of the
> IC is apparently damp with an oily liquid. There's a bulge in the
> surface of the IC, together with a few small cracks.
>
> Here's a question for you: Why would an IC suddenly do this?
>
> [And more importantly, how in the name of God does a device which only
> has access to a few milliwatts manage to get warm enough to physically
> melt??]
IC chips are almost always connected to the power supply (usually 5V)
and ground. If there is a shorted component in the IC, then the power
that briefly flows through the IC will be better measurable in watts,
and not milliwatts.
Regards,
John
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Here's an additional item of data: This particular IC has been switched
on 24/7 for approximately 8 years or so. [Except for the occasional shut
down now and then.]
I wonder what made it blow just now? Hmm, oh well! Pity it costs £497
for a new PCI board, eh? o_O
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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stbenge wrote:
> I guess these are the reasons I unplug my computer from both wall and
> phone line during a thunderstorm...
>
> Sam
Thet is a good idea!
I had bought two surge protectors one for my phone one for my PC.
With out me knowing the telephone line lost it's ground and the phone
surge protector acted as a ground. Luckily I only lost the modem when
the power surge came.
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Invisible wrote:
> Here's a question for you: Why would an IC suddenly do this?
In addition to what everyone else said, there's the effect of "thermal
runaway". Every semiconductor has a tiny leakage current, caused by
quantum effects, which is why devices use current even when not
switching. There's more leakage when the device gets hotter, because
there's more heat jiggling things around, basically. The more leakage,
the more current, the more heat, the more leakage .... >POP<
--
Darren New / San Diego, CA, USA (PST)
"That's pretty. Where's that?"
"It's the Age of Channelwood."
"We should go there on vacation some time."
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