IBM Returns to Water-cooling

I remember watching the installation of our first water-cooled mainframe at a bank in the late 70s (I was an operator keeping our other mainframes running during the project). I was initially skeptical (unconfined water is bad for electronics), but the performance of that box made a lot of converts. Water cooling went out of fashion as chips got smaller and dissipated less power per MIP Recently folks have started water cooling multiple components (CPU, graphics chip, memory, etc) in desktop PCs. It is interesting to see water cooling emerge as a green technology.

PC World - Business Center: IBM Updates High-end Servers, Returns to Water-cooling:
"IBM announced its most powerful Unix server to date Tuesday, an update to the System p5 595 that will be based on a new Power6 processor running at up to 5 GHz.

IBM also unveiled an update to its System p5 575 supercomputer that has a more efficient, water-based system to cool the processors. IBM hasn't used water-cooling in its servers since 1995, but it expects to use it increasingly as customers wrestle with a shortage of power to their datacenters.

The new systems, which will be discussed in detail at an IBM event in San Francisco Tuesday, continue a rebranding of IBM's servers that started last week. IBM said then that it was merging its System i and System p server lines into a single Power Systems family that can run IBM's AIX flavor of Unix, Linux or its i5/OS, now called i.

The new high-end machine, called the Power 595, is due for wide availability on May 6. Along with the faster processor it uses a new "point to point" interconnect technology to increase system bandwidth and get the most out of a system's processors, cache memory and main memory. It gives an aggregate memory bandwidth of 1.3 terabytes per second, IBM said.

The Power 595 supports up to 4 terabytes of memory, or twice that of the System p 595. The extra memory is good for handling very large databases, heavy transaction loads or consolidating servers. The system can run up to 254 virtualized partitions using IBM's PowerVM virtualization software.
. . .
The Power 575 supercomputer uses a new Hydro-Cluster design developed at IBM's research lab in Zurich. It uses a network of copper pipes that sit just above the processors and carry cold water to them and warm water away.

Water cooling is more efficient than air cooling -- 4,000 times more efficient, according to IBM -- and allowed the company to cram 448 4.7GHz Power6 processor cores in a Power 575 rack. That density would have been impossible using air cooling because customers don't have enough power in their datacenters to run the air conditioning units they would need, Handy said.

Joe Clabby [cq], president of Clabby Analytics in Yarmouth, Maine, said that at one time the hassle of setting up a water-cooled system outweighed the benefits. But rising energy costs mean it now makes economic sense to use water, because the cost of cooling air is becoming too great.

Handy said it's not so much a question of economics as the fact that customers simply can't get any more power into their datacenters. "It's not just that customers are going to save energy, it's that they are out of energy. They've hit a ceiling."
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The end goal is to reuse the hot water piped out of the computers in building heating systems, creating a "zero emissions datacenter." The researchers in Zurich are working now on how to pipe the water inside the chips, instead of over the top of them, making the cooling system more efficient, IBM said."

Using waste heat to warm buildings is more useful in Zurich than Phoenix. The Colorado School of Mines had a huge old computer in the early 70s that provided quite a lot of building heat when it was in use - it was not water cooled.