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From: JosephKK on 20 Jul 2010 01:38
On Mon, 19 Jul 2010 11:53:22 -0400, JW <none(a)dev.null> wrote:

>On Mon, 19 Jul 2010 03:19:26 -0700 JosephKK(a)yahoo.com wrote in Message id:
><mh8846p2fg81hi8tf3m8v2rmp3955n5prp(a)4ax.com>:
>
>>On Sat, 17 Jul 2010 08:35:54 +1000, Grant <omg(a)grrr.id.au> wrote:
>
>[...]
>
>>>PC with Core2 series CPU is running >100A regulator 3, 4, or 6 phase
>>>around the CPU area, lots of cooling air flow. But they're not trying
>>>to get that current off board, just direct it through a couple in^^2
>>>of CPU chip.
>>
>>Really? If the chip requires only 65 Watts how do you get to 100 A
>>even at 1.2 V?
>
>Some of the Quad cores have TDPs of 105W:
>http://ark.intel.com/ProductCollection.aspx?familyID=28398&MarketSegment=DT

Not a big surprise. Just the same a lot of power goes to the 1.8 V to
2.5 V north bridge interface. 1066 MHz memory interface is power
hungry.
From: JosephKK on 20 Jul 2010 01:43
On Tue, 20 Jul 2010 07:29:56 +1000, Grant <omg(a)grrr.id.au> wrote:

>On Mon, 19 Jul 2010 03:19:26 -0700, JosephKK(a)yahoo.com wrote:
>
>>On Sat, 17 Jul 2010 08:35:54 +1000, Grant <omg(a)grrr.id.au> wrote:
>>
>>>On Fri, 16 Jul 2010 09:03:11 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>>
>>>>On Fri, 16 Jul 2010 10:44:40 -0500, "Tim Williams"
>>>><tmoranwms(a)charter.net> wrote:
>>>>
>>>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:86t046tr9cu6p5n0f0c658sh1517m3p8so(a)4ax.com...
>>>>>> A small part like this doesn't conduct heat into pcb pours very well.
>>>>>> If you stick a part to a relatively thin thermally conductive sheet,
>>>>>> theta goes up as the part footprint area goes down [1].
>>>>><snip>
>>>>>> [1] anybody know the exact relation?
>>>>>
>>>>>Easy to approximate. Assume a circular footprint (cf. spherical chicken). Assume heat dissipation at the center is zero (fair for an infinnitessimal segment, blatantly false for an infinite number of them). If heat diffuses through copper out to infinity, temperature drops inversely with distance (because cross sectional area increases linearly). It looks like a point charge in space, and the temperature is defined by Gauss' law.
>>>>>
>>>>>Of course, heat diffuses through two or three means, with strange temperature-dependent coefficients besides. So it's not at all true that, the device itself, and the little bit of copper surrounding it that doesn't have a quite circular temperature profile, isn't dissipating any power. In fact, it could be dissipating a considerable amount of power. If the heat source were an infinnitessimal point, it would have infinite temperature, and therefore radiate infinite power density (power can still be finite, since the area is infinnitessimal).
>>>>>
>>>>>However, it is true that heat diffuses out, one way or another, so maybe the power dissipation is just a little higher in the center, and spreads out in a slightly-steeper-than-inverse relationship, eventually going to zero at infinity all the same. The trouble is deriving the exponent and coefficient of that power law.
>>>>>
>>>>>Tim
>>>>
>>>>Nice rant, but still no answer.
>>>>
>>>>Given a perfectly thermally conductive puck attached to an infinite
>>>>sheet of thin [1] finite-thermal-conductivity material, and assuming
>>>>conduction cooling only, what is the relationship of puck theta to
>>>>puck diameter?
>>>>
>>>>This is relevant to situations where you have a choice of, say, SOT89
>>>>versus DPAK versus D2PAK and you're heatsinking to copper foil.
>>>
>>>PC with Core2 series CPU is running >100A regulator 3, 4, or 6 phase
>>>around the CPU area, lots of cooling air flow. But they're not trying
>>>to get that current off board, just direct it through a couple in^^2
>>>of CPU chip.
>>
>>Really? If the chip requires only 65 Watts how do you get to 100 A
>>even at 1.2 V?
>
>Q6600 is 105W, I got one :)
>
>Grant.

Does it take the rather typical 3 or 4 supply voltages at various
currents? A lot of the high power is getting on/off chip (high speed
busses).

From: Grant on 20 Jul 2010 08:16
On Mon, 19 Jul 2010 22:43:14 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote:

>On Tue, 20 Jul 2010 07:29:56 +1000, Grant <omg(a)grrr.id.au> wrote:
>
>>On Mon, 19 Jul 2010 03:19:26 -0700, JosephKK(a)yahoo.com wrote:
>>
>>>On Sat, 17 Jul 2010 08:35:54 +1000, Grant <omg(a)grrr.id.au> wrote:
>>>
>>>>On Fri, 16 Jul 2010 09:03:11 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:
>>>>
>>>>>On Fri, 16 Jul 2010 10:44:40 -0500, "Tim Williams"
>>>>><tmoranwms(a)charter.net> wrote:
>>>>>
>>>>>>"John Larkin" <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in message news:86t046tr9cu6p5n0f0c658sh1517m3p8so(a)4ax.com...
>>>>>>> A small part like this doesn't conduct heat into pcb pours very well.
>>>>>>> If you stick a part to a relatively thin thermally conductive sheet,
>>>>>>> theta goes up as the part footprint area goes down [1].
>>>>>><snip>
>>>>>>> [1] anybody know the exact relation?
>>>>>>
>>>>>>Easy to approximate. Assume a circular footprint (cf. spherical chicken). Assume heat dissipation at the center is zero (fair for an infinnitessimal segment, blatantly false for an infinite number of them). If heat diffuses through copper out to infinity, temperature drops inversely with distance (because cross sectional area increases linearly). It looks like a point charge in space, and the temperature is defined by Gauss' law.
>>>>>>
>>>>>>Of course, heat diffuses through two or three means, with strange temperature-dependent coefficients besides. So it's not at all true that, the device itself, and the little bit of copper surrounding it that doesn't have a quite circular temperature profile, isn't dissipating any power. In fact, it could be dissipating a considerable amount of power. If the heat source were an infinnitessimal point, it would have infinite temperature, and therefore radiate infinite power density (power can still be finite, since the area is infinnitessimal).
>>>>>>
>>>>>>However, it is true that heat diffuses out, one way or another, so maybe the power dissipation is just a little higher in the center, and spreads out in a slightly-steeper-than-inverse relationship, eventually going to zero at infinity all the same. The trouble is deriving the exponent and coefficient of that power law.
>>>>>>
>>>>>>Tim
>>>>>
>>>>>Nice rant, but still no answer.
>>>>>
>>>>>Given a perfectly thermally conductive puck attached to an infinite
>>>>>sheet of thin [1] finite-thermal-conductivity material, and assuming
>>>>>conduction cooling only, what is the relationship of puck theta to
>>>>>puck diameter?
>>>>>
>>>>>This is relevant to situations where you have a choice of, say, SOT89
>>>>>versus DPAK versus D2PAK and you're heatsinking to copper foil.
>>>>
>>>>PC with Core2 series CPU is running >100A regulator 3, 4, or 6 phase
>>>>around the CPU area, lots of cooling air flow. But they're not trying
>>>>to get that current off board, just direct it through a couple in^^2
>>>>of CPU chip.
>>>
>>>Really? If the chip requires only 65 Watts how do you get to 100 A
>>>even at 1.2 V?
>>
>>Q6600 is 105W, I got one :)
>>
>>Grant.
>
>Does it take the rather typical 3 or 4 supply voltages at various
>currents? A lot of the high power is getting on/off chip (high speed
>busses).

I'm sure you can go find and read the specs as easily as I can.

Grant.
From: Uwe Hercksen on 20 Jul 2010 10:34


> The big boss had a codename that chip contest, which I won with the codename
> "Antares", with the series theme "Bright Stars". He made the comment in an
> email that he hoped it wasn't a comment about the power density. I replied
> (in an email) that the dual-core G5 had a power density of 1E9 times that of
> Sol.

Hello,

did you calculate the power density per surface area of the chip, or per
volume of the chip?

Bye

From: krw on 20 Jul 2010 17:51
On Tue, 20 Jul 2010 16:34:09 +0200, Uwe Hercksen
<hercksen(a)mew.uni-erlangen.de> wrote:

>
>
>> The big boss had a codename that chip contest, which I won with the codename
>> "Antares", with the series theme "Bright Stars". He made the comment in an
>> email that he hoped it wasn't a comment about the power density. I replied
>> (in an email) that the dual-core G5 had a power density of 1E9 times that of
>> Sol.
>
>Hello,
>
>did you calculate the power density per surface area of the chip, or per
>volume of the chip?

Volume.
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