Direct Die Cooling.. NO Heatsink....

Looks awesome. Even if it's not the most efficient it certainly has the biggest balls.
It sounds like this is just a rig you had extra. So what if it doesn't get a monster overclock.
The cool factor is worth it.
 
Dont work for me either :/

his bandwidth is probably maxed out :(

edit... nevermind
 
I am completely dis-assembleing my main water cooling loop today or tomorrow in order to test 3 motherboards and 3 processors for the maximum top speed reachable by any combination of the motherboards and processors.

I have:
DFI NFII Infinity Nforce2 board
Abit NF7-S Nforce 2 board
EPoX 8rda3+

Mobile Barton 2500
Mobile Barton 2400
Unlocked Barton 2500

I am trying to find the highest top speed I can reach with any of those board and CPU combinations

I was going to use a D-tek spiral block to do the testing, fo lack of a better block, but this direct die cooling has piqued my interest.

Can anybody point me to a helpful link with more information?
 
hmm..the dielectric fluid has better thermal capacity than water, would that mean that it would be a better coolant for even reguarl water cooling via heatsink?
 
This is all true but you fail to say which one works better. :p


DFI Daishi said:
well, in watercooling it's always a balance between surface area, and close contact between the hot core and the coolant.

direct die takes close contact to the max, but the surface area available for thermal transfer is teh suck.

as you ramp up an OC and start making more heat at the core, direct die temps go up more quickly than a well optimized waterblock wit lots of surface area.

direct die is cool. direct die works. it has different strengths and weeknesses than using a waterblock.
 
U235 said:
hmm..the dielectric fluid has better thermal capacity than water, would that mean that it would be a better coolant for even reguarl water cooling via heatsink?

No, there are other fluid properties that affect heat transfer properties, namely viscosity.
 
uclajd said:
This is all true but you fail to say which one works better. :p
what, because i have a doctorate in fluid and thermal mechanics? there are too many variables in the mix and a continuious variation between extremes for each, for me to preach one as clearly superior.

modern waterblocks are doing a pretty good job at cooling for the moment, and there is probably some fine tuning left in the technology. direct die is pretty exotic and relatively crude at the moment. what will come out ahead in the end? probably neither.

i have previosly expressed my view that before the speed race is over, CPUs will come with a heatspreader that is more like a water jacket, to circulate coolant through a fin or pin structure that is essentially a part of the core itself, but that might or might not happen, and who knows when things will go far enough for such measures to be cost effective?
 
Maybe this has already been addressed but isn't this technically direct-heatspreader rather than direct-die? The pics won't come up so I can't tell for sure.

I believe I've seen direct-die H20 on vr-zone or somewhere.

And I have seen direct-die phase-change, but that's just asking for the cracked die. :eek:
 
it's an athlon XP, so it has a bare core.

i have also seen direct die watercooling previously, but with water-antifreeze mix, and a block that sealed around the die rather than sealing around the chip package. non-conductive fluid really makes this project easier and less risky.
 
I've been wanting to try this for a long time. Does anyone know if the heatsink for the athlon 64's are removable or if they are soldered on like the P4?
 
mm177 said:
I've been wanting to try this for a long time. Does anyone know if the heatsink for the athlon 64's are removable or if they are soldered on like the P4?

You mean epoxied? Solder would never be strong enough... welding, perhaps, but they definately just epoxy it
 
ScHpAnKy said:
You mean epoxied? Solder would never be strong enough... welding, perhaps, but they definately just epoxy it

Sorry, poor choice of words. What Imeant is that the P4 is bonded (welded/permanently attached) to the IHS.
 
DFI Daishi said:
well, in watercooling it's always a balance between surface area, and close contact between the hot core and the coolant.

direct die takes close contact to the max, but the surface area available for thermal transfer is teh suck.

as you ramp up an OC and start making more heat at the core, direct die temps go up more quickly than a well optimized waterblock wit lots of surface area.

direct die is cool. direct die works. it has different strengths and weeknesses than using a waterblock.

When this topic comes up someone always mentions surface area of heatsink vs liquid.

Can someone explain this to me. The IHS makes contact with the top of the die with something in between (grease or whatever).

So the contact area is the top of the die? when you use direct cooling the contact area is the entire exposed part of the die top and 4 sides...right?

So how does that make the surface area for heat transfer better for the IHS?
 
mm177 said:
When this topic comes up someone always mentions surface area of heatsink vs liquid.

Can someone explain this to me. The IHS makes contact with the top of the die with something in between (grease or whatever).

So the contact area is the top of the die? when you use direct cooling the contact area is the entire exposed part of the die top and 4 sides...right?

So how does that make the surface area for heat transfer better for the IHS?
direct die means that there is not any IHS or anything else between the processor core and the cooling fluid.

normally watercooled processors conduct the heat that they produce to a metal waterblock, with thermal paste and sometime a IHS in between. once the metal of the waterblock is warmed up by the processor, the heat moves into the coolant being circulated through the block and away.

the waterblock has lots of surface area, but there is that added delta T from processor to waterblock before heat can move into the coolant and some added thermal resistance.

direct die has very little surface area, and the processor only has to be warmer than the coolant itself to move heat into the coolant and away.
 
Sorry no updates in a while guys....

My mom is very sick and other personal probs at the moment, been a little busy with all that...

But i did get the Abit nf7s mobo with Preacher Bios added and another stick of pc4000 for the test rig, I tried the OC some more, but still can't get to past 2.2ghz.... I think the procc just won't do it... I upped the voltage to 2.5v and it still won't budge anymore...

Some procc will oc good others won't.... I guess I got one that won't....

I was playing with my 1.2ghz Duron in there, and I got to 1.7ghz on the direct die, sorry no pics, I was just playing with it, and it is only a Duron...... might have got more, but like I said, it's only a Duron....


I will be posting these pics soon on my website, and will re-link them so they will be visable..

OH.. I also re-did the block as well, and put a reducer on the intake so it takes it from 1/2 down to 1/4 to increase the pressure, but it actually gave me higher temps than the original block.... go figure...

give me a couple days top get some things straightened out...
 
dracos said:
OH.. I also re-did the block as well, and put a reducer on the intake so it takes it from 1/2 down to 1/4 to increase the pressure, but it actually gave me higher temps than the original block.... go figure...

give me a couple days top get some things straightened out...

That's because you added tons of restricction to you loop and slowed down the flow. With fluid flow impinging directly onto a flat plate (CPU core) you're going to need as high a flowrate as you can get.
 
DFI Daishi said:
well, in watercooling it's always a balance between surface area, and close contact between the hot core and the coolant.

direct die takes close contact to the max, but the surface area available for thermal transfer is teh suck.

as you ramp up an OC and start making more heat at the core, direct die temps go up more quickly than a well optimized waterblock wit lots of surface area.

direct die is cool. direct die works. it has different strengths and weeknesses than using a waterblock.

Thats not entirely true. Your right in that surface area is important, but only when using a block. How much surface area do you think that copper or aluminum block has to the core? Instead of having to pull heat through a thermal paste and a metal buffer then to water, it is ALWAYS more efficient to apply your cooling fluid directly to the core itself.
The real key to making this successful is is moving the liquid that is immediately in contact with the core. With a low flow, a thin layer of water will linger close to the core due to friction. This layer is absorbing heat but it's not moving off fast enough to remove all the heat. You need to have your flow fast and pointed directly at the core to overcome this friction. This is the idea behind flow impingement. A high speed jet of water prevents that micro layer from lingering thus maximizing heat exchange.

If I were going to do direct die cooling, I would either make a nozzle that jetted water into the core or forced the water over the core in the same way Cather's cascade squeezes water through a narrow area around each jet.

Killernoodle; I did not know that water soaks into silicon like that. How did they find this out? (I haven't been reading up on PC cooling much lately)
 
cgrant26 said:
Thats not entirely true. Your right in that surface area is important, but only when using a block. How much surface area do you think that copper or aluminum block has to the core? Instead of having to pull heat through a thermal paste and a metal buffer then to water, it is ALWAYS more efficient to apply your cooling fluid directly to the core itself.
i elaborated on the point about the added heat transfer needed to go from the core to the waterblock, and then from the waterblock to the coolant in a later post. in a perfect world what you are saying is totally true. i think that the limitations imposed by using pumps that are readily available for watercooling in terms of size and price makes the situation a bit less clear cut.

cgrant26 said:
The real key to making this successful is is moving the liquid that is immediately in contact with the core. With a low flow, a thin layer of water will linger close to the core due to friction. This layer is absorbing heat but it's not moving off fast enough to remove all the heat. You need to have your flow fast and pointed directly at the core to overcome this friction. This is the idea behind flow impingement. A high speed jet of water prevents that micro layer from lingering thus maximizing heat exchange.
totally true. i just think that conventional pumps are not up to generating a flow impingement effect against the flat surface of the core. look at the orientation of the fins/pins in blocks that use jet impingement. they are oriented such that the jet goes along the length of the fin/pin generating the high turbulence region. it requires a lot less pumping power to make it happen on a surface like that than it does against the flat surface of the core oriented witht the flat side facing the nozzle. you might be able to tweak things to make it work with carefull nozzel design, and by orienting the nozzle on an angle, as opposed to being straight on to the processor, but i have not seen it done sucessfully in a home-brew direct die cooling system.

cgrant26 said:
If I were going to do direct die cooling, I would either make a nozzle that jetted water into the core or forced the water over the core in the same way Cather's cascade squeezes water through a narrow area around each jet.
props to you if you can make it work. i think that it would be tough to do well, but it would be awsome if you pull it off. maybe i am totally off base on all of this, but it would be interesting to hear what cathar has to say about setting up an impingement effect in this kind of system.

cgrant26 said:
Killernoodle; I did not know that water soaks into silicon like that. How did they find this out? (I haven't been reading up on PC cooling much lately)
i've never heard of it soaking into the silicon. i have heard about it soaking into the chip package and destroying the chip. i have even read one case where the core outright came off of the package.
 
Don't really need a massive flow rate to keep something cool. The problem, as always, is to do with convectional efficiency.

Water does hold a heck of a lot of heat per unit volume. 1 litre per minute (~0.3gpm) will rise in temperature by just 1.0C per 70W of heat. Could happily cool a 140W super-overclocked heat-monster CPU with just 1LPM, provided you can get the convectional rate up high enough.

This is where it all goes a little pear-shaped through. Silicon CPU dies are pretty small things. Achieving average convectional rates, via jet impingement, much above 50000W/m²K on a flat surface (cpu surfaces are flat of course) is very hard to do unless you're using pumps significantly stronger than what most people use for watercooling their computer.

Now at 50000W/m²K, with a 0.0001m² CPU (100mm²), results in a C/W of 0.20. Since we're talking direct-die here, this is pretty much what the cooling effect would be against our hypothetical 100mm² CPU. There's no metal conduction, and there's no thermal paste interface.

Let's compare that with some of the upper-end waterblocks.

The thermal paste barrier, per 100mm², with AS5 has been fairly accurately ascertained through a number of different methods over at Procooling, to have a C/W somewhere in the order 0.065 for a good mount (most estimates are coming in around 0.06-0.07, so we'll pick the middle average for now).

Now waterblocks, when looking at the convectional rate, can be stated in one of two ways. We can look at the actual convectional rate per unit of surface area that the water touches the metal, which is an incredibly complex way to model the waterblock's cooling effect, albeit the most accurate way to do so. Alternately we can utilise what is called the "effective convectional rate", which sums up the net effect of the additional surface area and all the little variances in cooling effect over that area, including the conductional costs of the metal in the block, and compacts it all down into what would be the "equivalent" convectional rate as if just acting on the area of what's being cooled (i.e. the CPU area)

By utilising the simpler "effective" cooling effect method, for a 100mm² CPU die, a block like the Storm/G4 is estimated to approach the 110000W/m²K mark, and the Storm/G5 approaches the 125000W/m²K mark, when matched with the uppish range end of water-cooling pumps that people use, but these values also include the conductional cost of the metal path as well.

At 110000W/m²K, the effective C/W for a 100mm² CPU is ~0.091C/W. For the thermal paste interface, the cost was 0.065, and these two are added together to arrive at an estimate of the total C/W for our 100mm² CPU, and it works out to ~0.156. At 125000W/m²K, it works out to around a 0.145 C/W.

Now in our direct die example, the C/W of a jet impingement device on a flat surface is 0.2, or substantially worse. In order to beat the waterblocks above we would need to achieve an average convectional effect of at least 70000W/m²K over the direct-die impingement of the CPU surface area.

This is where it gets a little difficult to construct such a device, and have it work with ordinary pumps. An jet impingement array, while good for larger areas, results in localised "dead-zones" where the jet washes meet. When impinging on a conductive plate of metal, this isn't so bad 'cos the metal just conducts the heat to where it's cooler, but when dealing with the surface of a CPU die we cannot afford this - the CPU will get MUCH hotter in these regions - which pretty much forces the single jet model for jet impingement cooling of a CPU die.

The other concern is the "wall" region of a jet impingement effect. The "wall" of a jet impingement effect occurs after about r=2.5d, where d is the diameter of the jet orifice. Once you get beyond the "wall" diameter, the convection efficiency drops off fairlu quickly. This places some important to consider restrictions on the size of the jet orifice. Ideally, in fact, the jet orifice should be tuned on a per-cpu-die basis.

For a 10x10mm CPU die, the diagonal area is ~14.14mm, which means that our jet orifice should at least be 14.14/5 = 2.83mm (7/64") in diameter, and the jet of course positioned centrally above the CPU die.

Using a variety of calculations which I won't get into here, the correspondent jet velocity for a jet of this size to achieve a net cooling effect > 65000W/m²K, is 11m/s.

Using yet further pressure drop calculations (which I also won't get into here), it all works out to requiring a pump that can deliver 4.7LPM (~1.25gpm) against a pressure resistance of around 9mH2O, and that's just for the waterblock alone. All up, we'd be talking about needing to use at least something like a US-Spec (60Hz) Iwaki MD-30RZ pump in order to deliver a cooling effect that would begin to outclass what top-end waterblocks can achieve.

If the die-size is larger then the problem becomes even harder to solve for the direct-die effect to achieve something better than what a good closed waterblock can achieve.

So the end answer is, yes, it can work IF you give it a strong enough pump (and by strong - we're talking REALLY strong), and you're blasting the bejeezus out of your small and fragile die of CPU silicon directly.

When coupled with all the other risks associated with direct-die cooling, my personal opinion on the matter is that it's simply not worth it.
 
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