autopsy of dead server
jgedge at amis.com
Sat Jun 4 18:04:41 MDT 2005
It's been a while since I've torn into PC architectures at this level...
but here's some info I gathered over the years.
A few years ago -- lightning struck the main office where I was
working. All the computers had Tripp-Lite ISO-BAR surge suppressors
between them and the building power-- some had UPS's attached between
the ISO-BAR and the computer. a few computers were still affected.
There were some SUN boxes [probably Ultra10's] that lost their network
cards. The surge supressors protected from HV event through the power
supply-- but the network cables running through the building acted like
huge anteanas to capture all the charge in the air from the lightnin.
With these computers-- a maintenance call where the network cards were
replaced solved the problem. In the case with Sun hardware-- the
HV/lightning damage was limitted to the network cards. I'm not sure how
PC's go in this area-- but if you didn't have a huge storm-- them this
likely not the cause.
As far as power supply causing trouble-- I've got some info on this. If
everything is fried -- but your processor still works-- it's probable
that something happened to the system power. I've seen cases where some
amateure hooks up power backwards [reverse power to the motherboard] and
everything on the board was smoked out except the processor [memory
might be salvagable also]. Reason: typically your computer power
supply has +12V, +5V, -5V supply. Back in the early `90's as cmos
geometries got smaller and smaller the supply power had to go down [for
the uP]. Partly due to physical breakdown of cmos transistors at
smaller feature sizes and partly because lowering the voltage helps with
reducing the power consumed [and heat dissipation through the chip]. To
accomodate these new processors that were at 3.3V and lower-- the
motherboards needed a new chip to regulate power for the uP and other
low voltage circuitry. Typically a drop out, or low drop out [LDO]
voltage regulator is used. Most LDO's [and voltage regulators in
general] are built on BJT [Bipolar technology NPN/PNP transistors]
instead of cmos technology. By it's very nature bipolar technology is
more immune to ESD [Electro Static Discharge]. The LDO in many cases
will tollerate ESD events better than a uP and most are designed to
protect downline power from reverse battery- power spikes, esd, etc...
so if your uP is good -- and everythign else went south on the server --
it's a good sign that your power supply went out-- or some other power
related event took the system out.
Jordan Curzon wrote:
>I have a computer that simply died. The motherboard won't boot and the
>two NICs that were on it give PCI errors in other boards. Any ideas as
>to how to determine post-mortem, what killed it?
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