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From: pigdos on 30 Sep 2006 01:35
First, I've discovered that the screwed-in, retaining clip on the back of
my X850xt is not the primary method by which force is applied to the GPU. If
you look closely at the X850xt there are two screws holding the copper
heatsink to the AL body of the assembly. These two screws are, in fact,
spring-loaded and determine (I beleive) how much force is applied to the
GPU. The retaining clip on the back merely holds the fansink assembly in
place.

On another note, I replaced the heat plate assembly on the back of my X850xt
with individual heatsinks. It probably makes some sort of difference because
the heat plate uses thermal pads that are attached to some sort of sticker
which is stuck on the heat plate.

I noticed the thermal pads you wrote about (the ones that interface the
front-side PCB memory to the heatsink). Those pads look so thick that they
must be insulating the memory on the front of the PCB rather than cooling
it, LOL. I'd imagine the reason my memory is incapable of running anywhere
near 600Mhz (which they are rated for) for sustained periods must be because
of these thick thermal pads. I wonder if the X850XT PE's feature
different/better thermal interfaces for their memory/GPU than the X850xt
does.

--
Doug


From: First of One on 30 Sep 2006 14:19
"pigdos" <NA(a)nowhere.com> wrote in message
news:DmnTg.6947$GR.6819(a)newssvr29.news.prodigy.net...
> First, I've discovered that the screwed-in, retaining clip on the back of
> my X850xt is not the primary method by which force is applied to the GPU.
> If you look closely at the X850xt there are two screws holding the copper
> heatsink to the AL body of the assembly. These two screws are, in fact,
> spring-loaded and determine (I beleive) how much force is applied to the
> GPU. The retaining clip on the back merely holds the fansink assembly in
> place.

Note that I don't have an X850XT, so I have been working off of photos here:
http://www.hardocp.com/article.html?art=NzYwLDEsLGhlbnRodXNpYXN0
and in particular this photo:
http://www.hardocp.com/image.html?image=MTExMzg0NzA1Mk4wSWtjeTZaYVhfMV8xMl9sLmpwZw==

I see two gold-colored standoffs, to which the retaining clip on the back of
the GPU screws in. There also appears to be two screw tips visible on two
corners of the copper inlay. I didn't know those were spring-loaded. This
means you can independently adjust the pressure applied to the GPU and RAM
chips, bringing the fansink closer to the board without crushing the GPU.

> On another note, I replaced the heat plate assembly on the back of my
> X850xt with individual heatsinks. It probably makes some sort of
> difference because the heat plate uses thermal pads that are attached to
> some sort of sticker which is stuck on the heat plate.

Individual RAM sinks will allow you to use a thin layer of thermal adhesive
instead of a pad, improving heat transfer. You may also want to do a 50/50
mix of adhesive and paste to get "removable strength".

Be prepared to see no difference, though, even after modifying the fansink
interface in the front. :-) As bad as a thick pad may be, the plastic RAM
chip package is probably doing more to insulate the silicon. Intel and AMD
went to the flip-chip design in the PIII days. ATi eventually followed suit
with the 9700 GPU. However, RAM is still packaged the old-fashioned way.

> I noticed the thermal pads you wrote about (the ones that interface the
> front-side PCB memory to the heatsink). Those pads look so thick that they
> must be insulating the memory on the front of the PCB rather than cooling
> it, LOL.

The pads were probably designed thick as a precaution, in anticipation for
large variation in RAM chip heights after mounting and soldering. If the RAM
chips are all at the same height (check with a steel ruler), you may be able
to replace the pads with paste, and bring the whole heat sink closer.

According to a Loctite engineer I worked with a few years ago, the thermal
resistance of thermal paste is actually 3-4x worse than aluminum, but
still orders of magnitude better than air. The purpose of the interface
material is to fill air gaps (both large and microscopic), nothing more.

> I wonder if the X850XT PE's feature different/better thermal interfaces
> for their memory/GPU than the X850xt does.

From what I remember, ATi doesn't market an AGP version of the X850XT, only
the XT-PE. The AGP X850XT is an effort from board partners like Sapphire or
Powercolor. If your fansink looks like the one pictured in the HardOCP
review, then the XT and XT-PE have identical cooling.

--
"War is the continuation of politics by other means.
It can therefore be said that politics is war without
bloodshed while war is politics with bloodshed."



From: pigdos on 30 Sep 2006 15:32
Speaking of Loctite, First, what would you think of using one of the Loctite
thread fastener compounds for attaching heatsinks? Some of the Loctite
products are designed to be used pre-assembly and others post-assembly but
all of them seem to have high temperature tolerances (somewhere over 100
degrees C).

Another question, I remember you mentioned that instead of increasing RAM
clocks I might be able to adjust the timings. I have some knowledge of this
(I studied memory technologies in college) so I'm assuming I'd have to use
some sort of BIOS editor. The thing is, if I guess wrong and tighten up the
timings too much, would this just make my X850xt into a doorstop?

Hope you're having a good weekend First.

--
Doug
"First of One" <daxinfx(a)yahoo.com> wrote in message
news:b-2dnXf9NtWOKIPYnZ2dnUVZ_sednZ2d(a)giganews.com...
>
> According to a Loctite engineer I worked with a few years ago, the thermal
> resistance of thermal paste is actually 3-4x worse than aluminum, but
> still orders of magnitude better than air. The purpose of the interface
> material is to fill air gaps (both large and microscopic), nothing more.
>
>> I wonder if the X850XT PE's feature different/better thermal interfaces
>> for their memory/GPU than the X850xt does.
>
> From what I remember, ATi doesn't market an AGP version of the X850XT,
> only
> the XT-PE. The AGP X850XT is an effort from board partners like Sapphire
> or
> Powercolor. If your fansink looks like the one pictured in the HardOCP
> review, then the XT and XT-PE have identical cooling.
>
> --
> "War is the continuation of politics by other means.
> It can therefore be said that politics is war without
> bloodshed while war is politics with bloodshed."
>
>
>


From: First of One on 30 Sep 2006 18:06
"pigdos" <NA(a)nowhere.com> wrote in message
news:_CzTg.6381$TV3.5995(a)newssvr21.news.prodigy.com...
> Speaking of Loctite, First, what would you think of using one of the
> Loctite thread fastener compounds for attaching heatsinks?

Loctite is primarily known for threadlocking, retaining and gasketing
compounds. The company also supplies the electronics industry with thermal
adhesives, TIM pads, die-attach encapsulants, etc., often with the
corresponding automated plant equipment. See:
<http://www.loctite.com/int_henkel/loctite_us/index.cfm?pageid=77&layout=2>

> Some of the Loctite products are designed to be used pre-assembly and
> others post-assembly but all of them seem to have high temperature
> tolerances (somewhere over 100 degrees C).

Yep, and this is what you want for a thermal adhesive. It wouldn't be nice
if the heat sink fell off at high temps, where it's most needed.

> Another question, I remember you mentioned that instead of increasing RAM
> clocks I might be able to adjust the timings. I have some knowledge of
> this (I studied memory technologies in college) so I'm assuming I'd have
> to use some sort of BIOS editor. The thing is, if I guess wrong and
> tighten up the timings too much, would this just make my X850xt into a
> doorstop?

I'm not sure if you need to touch the BIOS. ATiTool can be used to adjust
the RAM timings. Timing and overclocking settings can be included in the
same profile, loaded at Windows startup. Consequently, if your system
crashes, ATiTool just applies the default profile on the next startup.

--
"War is the continuation of politics by other means.
It can therefore be said that politics is war without
bloodshed while war is politics with bloodshed."



From: Barry Watzman on 30 Sep 2006 18:58
Do not use loctite. Sometimes it works too well. I've had laptops with
hard drives that were installed using it on the screws, and they had to
be drilled out to remove the hard drive. You could create such a
situation with a motherboard. In this instance (and I'd argue in the
case of the hard drives as well) loctite is a [bad] solution to a
problem that didn't exist.


pigdos wrote:

> Speaking of Loctite, First, what would you think of using one of the Loctite
> thread fastener compounds for attaching heatsinks? Some of the Loctite
> products are designed to be used pre-assembly and others post-assembly but
> all of them seem to have high temperature tolerances (somewhere over 100
> degrees C).
>
> Another question, I remember you mentioned that instead of increasing RAM
> clocks I might be able to adjust the timings. I have some knowledge of this
> (I studied memory technologies in college) so I'm assuming I'd have to use
> some sort of BIOS editor. The thing is, if I guess wrong and tighten up the
> timings too much, would this just make my X850xt into a doorstop?
>
> Hope you're having a good weekend First.
>
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