[RC5] power consumption

Relkin, Paul pwrelkin at mail.roanoke.edu
Mon Jul 2 17:37:51 EDT 2012

A 2012 Radeon HD 7970 GPU uses 215 additional watts when crunching RC5-72. Completing the rest of RC5-72 using only Radeon HD 7970s would consume 77 million kilowatt hours of electricity. If participants pay 10 cents per kilowatt hour, they would be donating $7.7 million of electricity. This would emit about 100 million pounds of carbon dioxide, as much as 5 million gallons of gas. Currently, most distributed.net clients are running on hardware that is less efficient than that.

Until 2009, RC5-72 ran entirely on CPUs rather than GPUs. In the first 6 years of RC5-72 (2002 to 2008), distributed.net caused thousands of CPUs to run at maximum power. The progress made by these CPUs is barely significant. The total keyspace completed before 2009 could now be processed in the same amount of time by only 38 Radeon HD 7970 GPUs, saving a lot of electricity.

I have participated in distributed.net since 2006 but I don't think it is ethical to continue crunching without evaluating the environmental impact. Processing speed and energy efficiency are improving exponentially. If distributed.net was paused for a few years, the cost to participants and the environment could be cut exponentially.

It's exciting that it is becoming increasingly feasible to crack RC5-72. But for now, I'm not sure that cracking the secret message a few years sooner is worth the environmental and economic consequences of crunching on the less efficient hardware available today.

Paul Relkin
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