"Jeff Liebermann" wrote in message
...
On Sat, 28 Aug 2010 02:04:07 +0100, "Arfa Daily"
wrote:

Thanks for the insights Jeff.

There was quite a bit of "Learn By Destroying(tm)" involved. Measuring
flatness and thermal resistance were a major exercise, but settled all
kinds of lab arguments.

Incidentally, you might be interested in how Arctic Silver works.
http://www.arcticsilver.com/products.htm
http://www.arcticsilver.com/msds.htm
Silver has a much higher thermal conductivity (410 W/m*K) as compared
to zinc oxide (21 W/m*K) and aluminum oxide (30 W/m*K) which is what's
in common thermal compound.
http://en.wikipedia.org/wiki/List_of_thermal_conductivities
However, if your shove an ohms-guesser into a puddle of Arctic Silver,
it's not conductive. That's because the particles of silver are so
far and few, that the bulk of the solution is polyolester or mineral
oil, which insulates the particles from each other, preventing mutual
contact. However, if you tear apart a CPU/heatsink that's been used
for a while, you'll notice that the Arctic Silver is a thick and dense
paste which is conductive. What has happened is that the polyol ester
mixture has evaporated sufficiently to provide contact between
particles. Since thermal conductivity is best through the silver
particles, the result is a superior thermal connection, with the
sliver particles filling the voids. You could do the same thing with
silver dust, but it would difficult to handle and apply. Meanwhile,
ordinary silicon grease does the same thing, but there's a difference.
The oil does not evaporate as easily, and the ceramic particles are
much larger and less compressible than the silver particles. Fewer
points of contact and lower thermal conductivity of ceramic, means a
worse thermal connection.

All interesting stuff. These are dedicated
games machines, not based on a PC in any way. The power supply is specced
to
deliver 12v at 23 amps, yes, that's twenty three amps ...

Almost all of this is potentially going into these two processors, so not
far off 300 watts between them. No mean task shifting the heat off them !

I don't believe it. The winner of the power hogging consumer CPU
contest was the DEC/Intel Alpha 21364 (EV79):
http://en.wikipedia.org/wiki/Alpha_21364
which burned 155 watts. Itanium II came close with 130 watts (per
core). I had an Alpha CPU machine to play with for a while, which
would burn my hand from the hot air coming out the back.

If you have a power line wattmeter or a Kill-A-Watt meter, I think a
measurement would be helpful.

--
Jeff Liebermann


Again, more interesting stuff Jeff. As to the power consumption of these
chips, see my reply to Jim above. Also, it is split between two chips, it's
actually not quite as much as 300 watts, and will of course be an 'on
demand' thing, depending on how hard the chips are being asked to work by
the processing task that's happening at the time, so the 23 amps is only a
worst case potential input current. However, that said, these two chips do
produce *very* considerable heat even when idling to produce nothing more
than the splash screen.

Arfa