[Beowulf] 96 cores in silent and small enclosure

[Mark Hahn]

> For instance, if the limit is the junction temperature, there's some thermal
> resistance between the reference junction and the measurement point, so if
> the chip is dissipating more, the delta T between limiting point and
> measurement point is greater.

and therefore the published max operating temp would be lower.

> work hotter or cooler.  (and a lot of times, those limits might be
> determined empirically... They test a bunch of cases, and that's what gets
> published in the data sheet)

no, I believe it's standard practice to characterize individual chips
as they're produced ("binning"), with specific markings (clock, temp range)
to communicate the results.

http://support.amd.com/us/Embedded_TechDocs/43374.pdf

has a number of tables that, for instance, define a thermal profile ("V")
which requires a Tcase max of 64C at 165W (!  though there aren't actually
any models listed in the doc rated to dissipate that much).  all the profiles
listed have a tcase-max of between 64 and 86C.

>> if you operate the chip within spec, you should expect the lifespan
>> to be plenty long (basically indefinite, but let's say 10 years...)
>
> Maybe, maybe not.  The chip life generally follows Arrhenius rule (roughly
> halving life for 10C rise), but it's hard to know what the "rated" life is,

hmm, I was assuming a lifetime warranty, but indeed, the terms are 3 years.
it would be surprising if you couldn't operate the chip within its thermal
spec, continuously, for 3 years, with low failure rates...