Heatsink fit for Intel 775 processor.

[Bob F]

I have an Intel E4300 Core 2 Duo processor I'm putting back into service. The
heatsink I have available is an Intel unit, but the copper contact point is
circular, and a bit smaller (1 1/8" in dia) than the top surface of the square
Intel processor. Will this heatsink have sufficient contact area, or does it
need to cover the entire top of the chip?

 

[Paul]

How much surface area of the IC would be left uncovered if you used it?
(since you didn't specify the size of the E4300)?

Well, I looked up the E4300, and from what I read, its package area is about
38 x 38 mm, which is about 1.5 inches by 1.5 inches, but this may not be the
actual amount available for heat sinking (?). If it is, that's a fair
amount of surface area that wouldn't be covered, so I expect it could be a
bit risky (meaning the potential for some possible hot spot regions for the
uncovered surface regions of the IC).

Overall, I'm sure there is some latitude here, but I don't know where you
find those statistics. But you could monitor the temperature with something
like Hard Disk Sentinel to check it. I think the best thing would be to
get a more suitable heat sink.

You would start by looking up the Core2 thermal spec. Page 56 shows
how a copper core Intel heatsink is constructed. The copper portion
is circular (presumably, to aid insertion of the copper within
the aluminum portion). This spec also mentions a difference in
thermal resistance, between processors with 2MB cache and 4MB cache,
so in fact there are two different die sizes.

http://download.intel.com/design/processor/designex/31780406.pdf

The die size is listed here as 143 square mm. If the die was
square, that would be 12mm on a side, or roughly half an inch
on each side. But we know it's not square, because for things
like quad cores, they need to put two dice in the same package,
and square die would not be the best for that. In any case,
if the contact point on your heatsink was less than
0.5*1.414 = 0.7" (17mm) in diameter, I'd be a bit worried. If
the copper portion is larger than that, you're OK.

http://www.anandtech.com/show/2045

Using "Core2 143mm" as search terms, I can find this article

http://www.zdnet.com/blog/hardware/inside-the-intel-core-2/45

It has a silicon die shot, but it doesn't say whether that is the
2MB or 4MB L2 cache version. You can take the aspect ratio
of this, and fit the numbers to make 143 square millimeters.

http://cdn-static.zdnet.com/i/story/60/52/000045/core2cpu.jpg

Being none too careful (to avoid scratching my LCD screen),
the die is roughly 4:3 aspect ratio. I didn't measure it
precisely.

Y 4
--- = --- X*Y=143 X*4X/3=143 X=10.3mm Y=13.8
X 3

Diameter-wise, that's a 3-4-5 triangle. Or just doing the
arithmetic SQRT( 10.3^2 + 13.8^2 ) = 17.2mm on the diagonal.

The rectangle should make the diagonal distance a bit longer.
I've checked my math, and my gut says that diagonal value
should be longer, but I've got no tool on this computer for
making scale drawings as a double check. So I improvise.
Using GIMP, I make two images with flood fill, then copy
them to a third image, rotating the square to roughly the
same diagonal as the rectangle. The square is 1200x1200 pixels,
the rectangle 1030x1380 pixels. The diagonal distance is only
slightly different. So 17.2mm diameter heatsink copper
core should cover it Anything bigger than that,
covers the "spreading angle" of the heat spreader on the
processor lid a little bit, but I doubt that contributed much
to the hot spot. The "thermal image" on the top of the processor,
will be slightly wider, due to the metal lid spreading the
heat a little bit.

http://img141.imageshack.us/img141/7761/gutcheck.gif

Have fun,
Paul

 

[Bob F]

You would start by looking up the Core2 thermal spec. Page 56 shows
how a copper core Intel heatsink is constructed. The copper portion
is circular (presumably, to aid insertion of the copper within
the aluminum portion). This spec also mentions a difference in
thermal resistance, between processors with 2MB cache and 4MB cache,
so in fact there are two different die sizes.

http://download.intel.com/design/processor/designex/31780406.pdf

The die size is listed here as 143 square mm. If the die was
square, that would be 12mm on a side, or roughly half an inch
on each side. But we know it's not square, because for things
like quad cores, they need to put two dice in the same package,
and square die would not be the best for that. In any case,
if the contact point on your heatsink was less than
0.5*1.414 = 0.7" (17mm) in diameter, I'd be a bit worried. If
the copper portion is larger than that, you're OK.

http://www.anandtech.com/show/2045

Using "Core2 143mm" as search terms, I can find this article

http://www.zdnet.com/blog/hardware/inside-the-intel-core-2/45

It has a silicon die shot, but it doesn't say whether that is the
2MB or 4MB L2 cache version. You can take the aspect ratio
of this, and fit the numbers to make 143 square millimeters.

http://cdn-static.zdnet.com/i/story/60/52/000045/core2cpu.jpg

Being none too careful (to avoid scratching my LCD screen),
the die is roughly 4:3 aspect ratio. I didn't measure it
precisely.

Y 4
--- = --- X*Y=143 X*4X/3=143 X=10.3mm Y=13.8
X 3

Diameter-wise, that's a 3-4-5 triangle. Or just doing the
arithmetic SQRT( 10.3^2 + 13.8^2 ) = 17.2mm on the diagonal.

The rectangle should make the diagonal distance a bit longer.
I've checked my math, and my gut says that diagonal value
should be longer, but I've got no tool on this computer for
making scale drawings as a double check. So I improvise.
Using GIMP, I make two images with flood fill, then copy
them to a third image, rotating the square to roughly the
same diagonal as the rectangle. The square is 1200x1200 pixels,
the rectangle 1030x1380 pixels. The diagonal distance is only
slightly different. So 17.2mm diameter heatsink copper
core should cover it Anything bigger than that,
covers the "spreading angle" of the heat spreader on the
processor lid a little bit, but I doubt that contributed much
to the hot spot. The "thermal image" on the top of the processor,
will be slightly wider, due to the metal lid spreading the
heat a little bit.

http://img141.imageshack.us/img141/7761/gutcheck.gif

Have fun,

Great post. Since it looked like the heatsink contact area would cover the
appropriate part of the chip, I went ahead and tried it. It seems to keep the
CPU appropriately cool. Many thanks to both Paul and Bill for their help.