IBM Water-Cools 3D Multi-Core Chip Stacks

An anonymous reader writes "Water cooling will enable multi-core processors to be stacked into 3D cubes, according to IBM's Zurich Research Laboratory which is demonstrating three-dimensional chip stacks. By stacking memory chips between processor cores IBM plans to multiply interconnections by 100 times while reducing their feature size tenfold. To cool the stack at a rate of 180 watts per layer, water flows down 50-micron channels between the stacked chips. Earlier this year, the same group described a copper-plate water cooling method for IBM's Hydro-Cluster supercomputer. The Zurich team predicts high-end IBM multicore computers will migrate from the copper-plate water-cooling-method to the 3-D chip-stack in five to 10 years." Reader Lilith's Heart-shape adds a link to the BBC's article on these internally-cooled chips.

180 Watts per layer

[javilon]

Sounds like too much, with typical numbers around 60 watts per processor this days.

Basic Physics of Thermoconduction

[mrbluze]

I thought you would want something with a low boiling point so you can move the heat as far away from the source as possible?

Something with a high specific heat is what's needed, which is why water is good. You can have any boiling point you like, depending on what pressure you apply to the liquid (boiling point is when vapour pressure = atmospheric pressure). If you are going to compress and decompress something to drive heat away, then use a gas.

Upgrades to cotrol systems needed

[kcbanner]

Right now, if the pump is off, or if the flow isn't flowing, the processor is none the wiser and happily starts up. I've seen my Core2Duo hit 100C when my pump died, my only warning was when the comp just shut off when it hit the temp cap. There needs to be some sort of control system that is actually linked in to the processor, so that it won't start if the flow of water through the block (or now the CPU itself) is below a certain rate. Most people who do use watercooling, however, know what they are doing and this usually isn't an issue, it would just be nice to know the server rack won't melt itself when someone blows the pump breaker.

It's quite the opposite

[mangu]

You don't want to cool with alcohol. The boiling point of most alcohols is between 60 and 80 degrees Celsius, as opposed to water's boiling point of 100 degrees Celsius.

Actually boiling removes much more heat than conduction. This is the principle used in heat pipes [wikipedia.org], where you want a low boiling temperature, because that will be the temperature in the hot side.

Re:Alcohol cooling is a bad idea.

[jeffmeden]

Only if you are making a wet/dry system, such as one that relies on phase change. If that's the case, it's refrigerant you want, and not alcohol (there is no real benefit to the vaporization unless the pressure swing is high). If you are doing closed loop all liquid, you want something that stays a liquid since vapor can't carry as much energy as liquid can given the same space. See automotive liquid cooling and refrigeration phase-change cooling for plenty of high-efficiency examples, none of which use alcohol or any similar substance.

Multicore resource portal

[Anonymous Coward]

If you like to read more information on multicore processors, go to http://www.multicoreinfo.com/ [multicoreinfo.com] .

Re:When will water cooling be feasible for ME?

[wattrlz]

... And is stacking the chips better than laying them flat and in a strip (like Pentium M)?

Sure. The interconnects could be shorter and thus impose much less lag. Core one wouldn't need to go through core two to talk to core three, etc.

Re:Alcohol cooling is a bad idea.

[Anonymous Coward]

the new R600a gas is Isobutane, also very flammable, but it's being used in many commercial fridges.

Re:When will water cooling be feasible for ME?

[nategoose]

Laying them out flat is better for cooling because it has more surface area, but the cube can be faster since the maximum distance from any 2 points within it is reduced from what it would be if the same chip area were laid out flat. This is why it NEEDS water cooling.

Re:Electrolysis

[X0563511]

Well, if they did use an exchanger there wouldn't be any water going into the chip... the chip would have a closed system filled with some crazy concoction instead... like some reactors use liquid sodium for instance (for for different reasons). Once outside of manufacturing and testing, it would likely be considered as a waterblock (or even a traditional heatsink/cooling system, if it was efficient enough). The big deal about in-die cooling is that you can make the die bigger without cooking the innards - without this new type of design you are limited to extracting heat directly out to the surface where the heatsink is.

Sorry, but I'm a tad bit excited by this - as I'm sure you can tell.

Re:CMOS = Power Efficient???

[NameIsDavid]

In those good old days, CMOS was efficient because a CMOS gate draws very little power when it is not switching. This leakage current could be very small in the old days when power supplies were 5V and thus transistor threshold voltages could be high enough to make leakage small. The power drawn during switching was the main component and was relatively small because clock speeds were low. Now, both static and dynamic power are high and even equal in modern chips. High clock speeds means high dynamic power. Scaled-down devices with 1V supplies means that there is no good threshold voltage that achieves both low leakage and the expected levels of high performance. Indeed, most technologies offer multiple threshold voltages to at least let the circuit designer use a high-performance or low-leakage device in any given circuit, depending on the needs of that circuit.

Re:Alcohol cooling is a bad idea.

[AliasMarlowe]

The boiling point of most alcohols is between 60 and 80 degrees Celsius, as opposed to water's boiling point of 100 degrees Celsius.

Most alcohols? Or maybe just two: at atmospheric pressure methanol boils at 64.7 C and ethanol at 78 C, but here are some of the others, all with higher boiling points:
tert-butanol 82.4 C
2-propanol 82.7 C
2-methyl-2-propanol 83 C
2-butanol 94 C
1-propanol 97 C
2-methyl-2-butanol 102 C
2-methyl-1-propanol 108 C
1-butanol 117.7 C
2-methoxyethanol 124 C
3-methyl-1-butanol 130 C
2-hexanol 136 C
1-pentanol 138 C
1-hexanol 151.4 C
2-butoxyethanol 171 C
1-heptanol 176 C
1-octanol 195 C
1-nonanol 215 C (freezing point is -7 C)
1-decanol 231 C (freezing point is +7 C)
The boiling point of 1-octanol is pretty good, so it could be used to cool reliably at higher temperatures than water. Also, its viscosity is only one quarter that of water, so it can be pumped through narrow channels more easily (higher flow at lower pressure) to achieve higher heat removal. It remains liquid down to -16 C, so it would not have to be purged from the chip for storage in cool environments.

Re:water?

[Anonymous Coward]

liquid water doesn't change density for any reason ever, dumbass.

-1, Wrong

From wikipedia [wikipedia.org] (or any grade school chemistry book):

At room temperature, liquid water becomes denser with lowering temperature, just like other substances. But at 4C (3.98 more precisely), just above freezing, water reaches its maximum density, and as water cools further toward its freezing point, the liquid water, under standard conditions, expands to become less dense.