Substantial board flex after installing P4 3.4 heat sink in Socket 775 (P5AD2-E PREM): OK OR NOT?

Hi,

I am putting together a new machine with an ASUS P5AD2E Premium. I
installed the processor in the 775 socket and all went well. When I
put the heat sink on, I heard "crunchy" noises. Later I had to remove
the board because I had to do a case mod to make a power supply fit
and I noticed that there was quite a bit of flex underneath the CPU.
It wasn't pretty and I am concerned.

Is this typical of these boards to flex this way?

 

The Pentium 4 heatsinks normally do introduce a noticeable flex in the
motherboard - the reason being to prevent any shock (i.e. drop) from
pulling the CPU socket off the motherboard.

 

Thats a relief... thanks.

I'm powered up and installing windows so all is going well!


Thanks again,
Tony

 

You can see some of Intel's thinking in this slide set:
ftp://download.intel.com/design/Pentium4/guides/29072801.pdf

They like a high normal force, as they are assuming you
will be using the provided phase change material already
on the heatsink. If you use thermal paste, that doesn't need
as much normal force to work properly.

Even though I've read this slide set and understand it,
that has not stopped me from using third party heatsink/fan
assemblies that don't stress the board quite as much. There
are even some heatsinks that provide a backing plate, that
goes behind the processor socket area.

Since there doesn't seem to be an epidemic of dead boards
out there, that seems to back up Intel's analysis of the
mechanical loading. I was always taught it was not a good
idea to put solder under stress (mainly the solder balls
underneath ball grid array chips), but I guess Intel knows
more than I do.

Paul

 

The BGA separating from the board was my first thought when I heard
those crunchy-pingy sounds. What Fan/Sink assy would you reccomend for
a P4 3.4 Socket 775?

I saw one by Asus that looked really cool, like a jet engine of sorts.

Tony
p.s. My CPU temperature is around 60 or so.

 

I don't have any LGA775 boards here, but I have a Zalman 7000
AlCu on a S462 and a S478 board. You can also get an adapter
kit for the Zalman 7000, to fit it to an LGA775 board.

http://www.newegg.com/app/ViewProductDesc.asp?description=35-118-219&depa=0
http://www.newegg.com/app/ViewProductDesc.asp?description=35-118-112&depa=0

There is also the Zalman 7700, which is a larger heatsink.

http://www.newegg.com/app/ViewProductDesc.asp?description=35-118-114&depa=0

The 7000 needs a mechanical clearance radius of 55mm, and the
7700 needs 68mm. Usually, this means the Zalman bumps into the
power supply. You need to check the Zalman web site, as they have
some compatibility lists, but it doesn't hurt to check the
dimensions of the board itself.

There are also the Thermaltake XP-90 and XP-120.
Fan is sold separately. These are relatively light, so shouldn't
strain the mounting.

http://www.overclockers.com/articles1094/ (Review of the XP-90)
http://www.overclockers.com/articles1043/ (Review of the XP-120)
http://www.silentpcreview.com/article194-page1.html (XP-90 review)

http://www.thermalright.com/a_page/main_product_accessories.htm#acc_775
http://www.thermalright.com/a_page/main_support_installation_lga775.htm

Note in the XP-120 review, the heatsink has overhang issues like
both of the Zalman heatsinks. This is an unfortunate fact of life
with high performance heatsinks. If you buy a heatsink that fits
within the profile of the socket, performance will be no better than
the Intel HSF.

XP-120 0.18C/W with inaudible fan
XP-90 0.18C/W with inaudible fan
Zalman 7000B 0.22C/W with fan at full speed (reasonably quiet)
Zalman 7700 0.21C/W with fan at full speed (reasonably quiet)

http://www.zalman.co.kr/eng/product/view.asp?idx=142&code=005009
http://www.zalman.co.kr/eng/product/view.asp?idx=146&code=005009

To compare numbers, here is an Intel S478 retail HSF 0.33C/W
http://www.silentpcreview.com/article138-page1.html

If a processor kicks out 89W, then the Intel solution gives a
29.4C delta between case air temp and processor temp. The other
cooling products will give a lower temperature rise, without an
excess of noise. And the noise is the main reason to want one.

As one of the reviews mentions above, the Thermaltake designs use
clips. The Zalmans use screws, which is a bit easier to deal with.

I don't recommend the use of "tower" coolers or any of the
other "big blob" type designs. Many of them, while they use heat
pipes, have inferior construction (heatpipe joins to base with
thermal paste and not a nice mechanical heat path), and they put
a lot of strain on the motherboard. In the case of one tower product,
it gets very close to the side panel of the computer. None of the
reviews I've read yet, suggest they have thermal performance
to rival the examples above. A good heatsink design keeps most of
its mass as near to the motherboard as possible, to reduce the
twisting force from the weight.

Regarding the overhang issue, I've taken pictures of the motherboard
for my P4C800-E and A7N8X-E manuals, into my favorite drawing tool,
and worked out how much clearance is required to use it (with the
Zalmans). The problem with the P5AD2-E is that Asus is no longer
putting a picture of the product in the manual. At least the Zalman
site has this info, and it says you need 14.5mm from the motherboard
to the PSU for the 7700 when used on the P5AD2-E. For any of the
heatsinks, you should check that the Northbridge and the DIMMs are
cleared by the heatsink, as well. In one review, the XP-120 got
pretty close to the Northbridge heatsink.

Here is one of the Zalman compatibility lists.
http://www.zalman.co.kr/product/cooler/7700-775MBlist_eng.htm

And for the sake of completeness, here is an example of a heatsink
that stays pretty well within the confines of the processor area.
With low fan setting, about 0.25C/W, 620g weight, $55 without fan.
I like the look of these, just for the finish of the base.

http://www.swiftnets.com/products/mcx775-V.asp

HTH,
Paul

 

I am using the Thermaltake Jungle on my 3.4 and it works well once I
fixed my airflow problem. My temperatures were like yours with my first
case as the heat sink was less than an inch from the power supply. I
replaced the case with a Raidmax one that has close to 2" clearance.
This dropped my idle temperatures to the low 40s. With the first case
you could feel the heat of the power supply through the side of the case
so much heat was being dumped into it. The placement of the heat sink
made my other rear exhaust fan worthless.

 

Did you get your temps to 40 with the stock heat sink or the
thermaltake jungle? Reason I ask is because my power supply is
isolated from the rest of the machine.

http://www.newegg.com/app/ViewProductDesc.asp?description=11-112-510&depa=1

 

The Thermaltake didn't seem to be much different from the Intel heat
sink so I don't think it had much affect. I tried it after I couldn't
get the temperature down with the Intel heat sink. Until I replaced the
case with one with much better airflow the temperatures stayed in the
50s even at idle. My new case has three exhaust fans surrounding the
heat sink plus the power supply and top fans so I don't have the hot
spot I had before.